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	$142.25	12.618%	$160.1991	$160.20	$160.20	$160.20
Purchase #2	$89.76	13.127%	$101.5428	$101.54	$101.55	$101.50
Purchase #3	$149.59	10.778%	$165.7128	$165.71	$165.70	$165.70
Purchase #4	$216.39	4.678%	$226.5127	$226.51	$226.50	$226.50
Purchase #5	$59.81	6.848%	$63.9058	$63.91	$63.90	$63.90
Purchase #6	$233.27	4.404%	$243.5432	$243.54	$243.55	$243.50
Purchase #7	$57.76	6.286%	$61.3908	$61.39	$61.40	$61.40
7 purchase totals =	$948.83		$1,022.8072	$1,022.80	$1,022.80	$1,022.70