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	$101.98	12.651%	$114.8815	$114.88	$114.90	$114.90
Purchase #2	$165.65	12.496%	$186.3496	$186.35	$186.35	$186.30
Purchase #3	$118.78	6.182%	$126.123	$126.12	$126.10	$126.10
Purchase #4	$144.28	12.468%	$162.2688	$162.27	$162.25	$162.30
Purchase #5	$7.54	9.349%	$8.2449	$8.24	$8.25	$8.20
Purchase #6	$235.70	9.325%	$257.679	$257.68	$257.70	$257.70
Purchase #7	$245.54	4.404%	$256.3536	$256.35	$256.35	$256.40
7 purchase totals =	$1,019.47		$1,111.9004	$1,111.89	$1,111.90	$1,111.90