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	$91.96	10.519%	$101.6333	$101.63	$101.65	$101.60
Purchase #2	$57.51	3.115%	$59.3014	$59.30	$59.30	$59.30
Purchase #3	$248.66	4.816%	$260.6355	$260.64	$260.65	$260.60
Purchase #4	$37.85	4.519%	$39.5604	$39.56	$39.55	$39.60
Purchase #5	$179.90	9.317%	$196.6613	$196.66	$196.65	$196.70
Purchase #6	$133.50	4.433%	$139.4181	$139.42	$139.40	$139.40
Purchase #7	$36.38	3.728%	$37.7362	$37.74	$37.75	$37.70
7 purchase totals =	$785.76		$834.9462	$834.95	$834.95	$834.90