Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$111.75	10.223%	$123.1742	$123.17	$123.15	$123.20
Purchase #2	$147.75	8.443%	$160.2245	$160.22	$160.20	$160.20
Purchase #3	$91.91	10.838%	$101.8712	$101.87	$101.85	$101.90
Purchase #4	$136.42	7.132%	$146.1495	$146.15	$146.15	$146.10
Purchase #5	$218.87	10.861%	$242.6415	$242.64	$242.65	$242.60
Purchase #6	$97.31	8.260%	$105.3478	$105.35	$105.35	$105.30
Purchase #7	$125.34	13.424%	$142.1656	$142.17	$142.15	$142.20
7 purchase totals =	$929.35		$1,021.5743	$1,021.57	$1,021.50	$1,021.50