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	$156.41	4.142%	$162.8885	$162.89	$162.90	$162.90
Purchase #2	$181.25	6.216%	$192.5165	$192.52	$192.50	$192.50
Purchase #3	$204.31	3.165%	$210.7764	$210.78	$210.80	$210.80
Purchase #4	$248.74	6.864%	$265.8135	$265.81	$265.80	$265.80
Purchase #5	$54.69	9.311%	$59.7822	$59.78	$59.80	$59.80
Purchase #6	$6.96	10.483%	$7.6896	$7.69	$7.70	$7.70
Purchase #7	$116.53	6.818%	$124.475	$124.48	$124.50	$124.50
7 purchase totals =	$968.89		$1,023.9417	$1,023.95	$1,024.00	$1,024.00