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	$115.58	7.363%	$124.0902	$124.09	$124.10	$124.10
Purchase #2	$71.67	11.228%	$79.7171	$79.72	$79.70	$79.70
Purchase #3	$189.62	3.787%	$196.8009	$196.80	$196.80	$196.80
Purchase #4	$55.54	6.265%	$59.0196	$59.02	$59.00	$59.00
Purchase #5	$153.93	10.202%	$169.6339	$169.63	$169.65	$169.60
Purchase #6	$190.60	10.380%	$210.3843	$210.38	$210.40	$210.40
Purchase #7	$196.85	4.267%	$205.2496	$205.25	$205.25	$205.20
7 purchase totals =	$973.79		$1,044.8956	$1,044.89	$1,044.90	$1,044.80