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	$113.92	12.304%	$127.9367	$127.94	$127.95	$127.90
Purchase #2	$180.91	6.200%	$192.1264	$192.13	$192.15	$192.10
Purchase #3	$101.29	10.467%	$111.892	$111.89	$111.90	$111.90
Purchase #4	$250.83	6.505%	$267.1465	$267.15	$267.15	$267.10
Purchase #5	$221.30	10.724%	$245.0322	$245.03	$245.05	$245.00
Purchase #6	$6.76	5.323%	$7.1198	$7.12	$7.10	$7.10
Purchase #7	$48.75	11.125%	$54.1734	$54.17	$54.15	$54.20
7 purchase totals =	$923.76		$1,005.4270	$1,005.43	$1,005.45	$1,005.30