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	$53.61	11.431%	$59.7382	$59.74	$59.75	$59.70
Purchase #2	$93.70	13.482%	$106.3326	$106.33	$106.35	$106.30
Purchase #3	$10.93	3.142%	$11.2734	$11.27	$11.25	$11.30
Purchase #4	$184.32	11.708%	$205.9002	$205.90	$205.90	$205.90
Purchase #5	$197.35	3.223%	$203.7106	$203.71	$203.70	$203.70
Purchase #6	$93.97	4.171%	$97.8895	$97.89	$97.90	$97.90
Purchase #7	$96.69	3.527%	$100.1003	$100.10	$100.10	$100.10
7 purchase totals =	$730.57		$784.9448	$784.94	$784.95	$784.90