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	$59.55	13.621%	$67.6613	$67.66	$67.65	$67.70
Purchase #2	$16.78	10.267%	$18.5028	$18.50	$18.50	$18.50
Purchase #3	$28.75	7.217%	$30.8249	$30.82	$30.80	$30.80
Purchase #4	$247.92	8.328%	$268.5668	$268.57	$268.55	$268.60
Purchase #5	$223.43	8.496%	$242.4126	$242.41	$242.40	$242.40
Purchase #6	$226.45	12.658%	$255.114	$255.11	$255.10	$255.10
Purchase #7	$81.69	4.534%	$85.3938	$85.39	$85.40	$85.40
7 purchase totals =	$884.57		$968.4762	$968.46	$968.40	$968.50