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	$71.55	3.861%	$74.3125	$74.31	$74.30	$74.30
Purchase #2	$77.32	11.432%	$86.1592	$86.16	$86.15	$86.20
Purchase #3	$36.64	10.456%	$40.4711	$40.47	$40.45	$40.50
Purchase #4	$191.50	11.445%	$213.4172	$213.42	$213.40	$213.40
Purchase #5	$37.83	7.560%	$40.6899	$40.69	$40.70	$40.70
Purchase #6	$186.91	5.344%	$196.8985	$196.90	$196.90	$196.90
Purchase #7	$157.26	10.656%	$174.0176	$174.02	$174.00	$174.00
7 purchase totals =	$759.01		$825.9660	$825.97	$825.90	$826.00