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	$81.25	4.677%	$85.0501	$85.05	$85.05	$85.10
Purchase #2	$76.58	5.766%	$80.9956	$81.00	$81.00	$81.00
Purchase #3	$111.51	12.673%	$125.6417	$125.64	$125.65	$125.60
Purchase #4	$49.42	13.665%	$56.1732	$56.17	$56.15	$56.20
Purchase #5	$237.57	4.861%	$249.1183	$249.12	$249.10	$249.10
Purchase #6	$191.68	4.648%	$200.5893	$200.59	$200.60	$200.60
Purchase #7	$187.61	11.854%	$209.8493	$209.85	$209.85	$209.80
7 purchase totals =	$935.62		$1,007.4175	$1,007.42	$1,007.40	$1,007.40