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	$70.48	4.478%	$73.6361	$73.64	$73.65	$73.60
Purchase #2	$216.90	3.413%	$224.3028	$224.30	$224.30	$224.30
Purchase #3	$210.96	8.430%	$228.7439	$228.74	$228.75	$228.70
Purchase #4	$37.39	8.330%	$40.5046	$40.50	$40.50	$40.50
Purchase #5	$247.30	9.140%	$269.9032	$269.90	$269.90	$269.90
Purchase #6	$79.89	11.735%	$89.2651	$89.27	$89.25	$89.30
Purchase #7	$124.32	3.751%	$128.9832	$128.98	$129.00	$129.00
7 purchase totals =	$987.24		$1,055.3389	$1,055.33	$1,055.35	$1,055.30