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	$157.52	7.492%	$169.3214	$169.32	$169.30	$169.30
Purchase #2	$218.28	6.799%	$233.1209	$233.12	$233.10	$233.10
Purchase #3	$151.93	10.233%	$167.477	$167.48	$167.50	$167.50
Purchase #4	$53.54	11.748%	$59.8299	$59.83	$59.85	$59.80
Purchase #5	$134.28	9.148%	$146.5639	$146.56	$146.55	$146.60
Purchase #6	$122.43	3.526%	$126.7469	$126.75	$126.75	$126.70
Purchase #7	$197.97	12.782%	$223.2745	$223.27	$223.25	$223.30
7 purchase totals =	$1,035.95		$1,126.3345	$1,126.33	$1,126.30	$1,126.30