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	$189.58	10.861%	$210.1703	$210.17	$210.15	$210.20
Purchase #2	$84.94	5.197%	$89.3543	$89.35	$89.35	$89.40
Purchase #3	$168.92	6.374%	$179.687	$179.69	$179.70	$179.70
Purchase #4	$230.48	10.669%	$255.0699	$255.07	$255.05	$255.10
Purchase #5	$143.98	8.435%	$156.1247	$156.12	$156.10	$156.10
Purchase #6	$201.77	4.686%	$211.2249	$211.22	$211.20	$211.20
Purchase #7	$119.77	6.503%	$127.5586	$127.56	$127.55	$127.60
7 purchase totals =	$1,139.44		$1,229.1897	$1,229.18	$1,229.10	$1,229.30