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	$124.93	4.843%	$130.9804	$130.98	$131.00	$131.00
Purchase #2	$168.74	10.746%	$186.8728	$186.87	$186.85	$186.90
Purchase #3	$192.50	9.470%	$210.7298	$210.73	$210.75	$210.70
Purchase #4	$95.30	9.637%	$104.4841	$104.48	$104.50	$104.50
Purchase #5	$147.69	11.227%	$164.2712	$164.27	$164.25	$164.30
Purchase #6	$78.89	13.785%	$89.765	$89.77	$89.75	$89.80
Purchase #7	$74.26	9.348%	$81.2018	$81.20	$81.20	$81.20
7 purchase totals =	$882.31		$968.3051	$968.30	$968.30	$968.40