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	$182.42	9.755%	$200.2151	$200.22	$200.20	$200.20
Purchase #2	$40.30	10.374%	$44.4807	$44.48	$44.50	$44.50
Purchase #3	$170.46	11.123%	$189.4203	$189.42	$189.40	$189.40
Purchase #4	$245.40	10.588%	$271.383	$271.38	$271.40	$271.40
Purchase #5	$176.32	12.157%	$197.7552	$197.76	$197.75	$197.80
Purchase #6	$228.87	10.701%	$253.3614	$253.36	$253.35	$253.40
Purchase #7	$37.89	6.445%	$40.332	$40.33	$40.35	$40.30
7 purchase totals =	$1,081.66		$1,196.9477	$1,196.95	$1,196.95	$1,197.00