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	$32.57	11.498%	$36.3149	$36.31	$36.30	$36.30
Purchase #2	$194.66	8.130%	$210.4859	$210.49	$210.50	$210.50
Purchase #3	$151.32	13.421%	$171.6287	$171.63	$171.65	$171.60
Purchase #4	$197.91	5.738%	$209.2661	$209.27	$209.25	$209.30
Purchase #5	$224.77	4.755%	$235.4578	$235.46	$235.45	$235.50
Purchase #6	$116.97	6.774%	$124.8935	$124.89	$124.90	$124.90
Purchase #7	$144.32	8.646%	$156.7979	$156.80	$156.80	$156.80
7 purchase totals =	$1,062.52		$1,144.8448	$1,144.85	$1,144.85	$1,144.90