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	$202.57	6.365%	$215.4636	$215.46	$215.45	$215.50
Purchase #2	$166.32	4.587%	$173.9491	$173.95	$173.95	$173.90
Purchase #3	$212.63	12.234%	$238.6432	$238.64	$238.65	$238.60
Purchase #4	$217.89	7.351%	$233.9071	$233.91	$233.90	$233.90
Purchase #5	$22.71	13.629%	$25.8051	$25.81	$25.80	$25.80
Purchase #6	$139.56	8.359%	$151.2258	$151.23	$151.25	$151.20
Purchase #7	$147.48	12.489%	$165.8988	$165.90	$165.90	$165.90
7 purchase totals =	$1,109.16		$1,204.8927	$1,204.90	$1,204.90	$1,204.80