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	$48.85	6.666%	$52.1063	$52.11	$52.10	$52.10
Purchase #2	$110.29	4.371%	$115.1108	$115.11	$115.10	$115.10
Purchase #3	$125.61	4.519%	$131.2863	$131.29	$131.30	$131.30
Purchase #4	$71.74	9.700%	$78.6988	$78.70	$78.70	$78.70
Purchase #5	$85.57	6.227%	$90.8984	$90.90	$90.90	$90.90
Purchase #6	$116.80	8.361%	$126.5656	$126.57	$126.55	$126.60
Purchase #7	$82.70	13.717%	$94.044	$94.04	$94.05	$94.00
7 purchase totals =	$641.56		$688.7102	$688.72	$688.70	$688.70