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	$64.67	5.620%	$68.3045	$68.30	$68.30	$68.30
Purchase #2	$198.33	12.421%	$222.9646	$222.96	$222.95	$223.00
Purchase #3	$64.50	11.471%	$71.8988	$71.90	$71.90	$71.90
Purchase #4	$149.27	4.857%	$156.52	$156.52	$156.50	$156.50
Purchase #5	$19.62	5.308%	$20.6614	$20.66	$20.65	$20.70
Purchase #6	$191.59	13.838%	$218.1022	$218.10	$218.10	$218.10
Purchase #7	$38.43	8.143%	$41.5594	$41.56	$41.55	$41.60
7 purchase totals =	$726.41		$800.0109	$800.00	$799.95	$800.10