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	$62.98	4.736%	$65.9627	$65.96	$65.95	$66.00
Purchase #2	$207.30	7.335%	$222.5055	$222.51	$222.50	$222.50
Purchase #3	$79.86	12.344%	$89.7179	$89.72	$89.70	$89.70
Purchase #4	$152.51	9.560%	$167.09	$167.09	$167.10	$167.10
Purchase #5	$224.33	11.394%	$249.8902	$249.89	$249.90	$249.90
Purchase #6	$91.86	11.428%	$102.3578	$102.36	$102.35	$102.40
Purchase #7	$186.61	7.697%	$200.9734	$200.97	$200.95	$201.00
7 purchase totals =	$1,005.45		$1,098.4975	$1,098.50	$1,098.45	$1,098.60