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	$160.41	6.787%	$171.297	$171.30	$171.30	$171.30
Purchase #2	$7.76	3.843%	$8.0582	$8.06	$8.05	$8.10
Purchase #3	$203.65	5.629%	$215.1135	$215.11	$215.10	$215.10
Purchase #4	$160.49	5.389%	$169.1388	$169.14	$169.15	$169.10
Purchase #5	$82.29	9.232%	$89.887	$89.89	$89.90	$89.90
Purchase #6	$223.89	9.495%	$245.1484	$245.15	$245.15	$245.10
Purchase #7	$74.81	13.625%	$85.0029	$85.00	$85.00	$85.00
7 purchase totals =	$913.30		$983.6458	$983.65	$983.65	$983.60