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	$197.70	12.196%	$221.8115	$221.81	$221.80	$221.80
Purchase #2	$139.90	10.168%	$154.125	$154.13	$154.15	$154.10
Purchase #3	$83.98	6.181%	$89.1708	$89.17	$89.15	$89.20
Purchase #4	$125.77	7.522%	$135.2304	$135.23	$135.25	$135.20
Purchase #5	$156.50	4.304%	$163.2358	$163.24	$163.25	$163.20
Purchase #6	$145.77	4.315%	$152.06	$152.06	$152.05	$152.10
Purchase #7	$89.29	13.397%	$101.2522	$101.25	$101.25	$101.30
7 purchase totals =	$938.91		$1,016.8857	$1,016.89	$1,016.90	$1,016.90