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	$93.32	13.148%	$105.5897	$105.59	$105.60	$105.60
Purchase #2	$147.73	11.322%	$164.456	$164.46	$164.45	$164.50
Purchase #3	$5.38	3.132%	$5.5485	$5.55	$5.55	$5.50
Purchase #4	$133.60	9.397%	$146.1544	$146.15	$146.15	$146.20
Purchase #5	$77.83	9.603%	$85.304	$85.30	$85.30	$85.30
Purchase #6	$77.66	10.121%	$85.52	$85.52	$85.50	$85.50
Purchase #7	$101.97	4.606%	$106.6667	$106.67	$106.65	$106.70
7 purchase totals =	$637.49		$699.2393	$699.24	$699.20	$699.30