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	$177.47	12.778%	$200.1471	$200.15	$200.15	$200.10
Purchase #2	$53.26	3.554%	$55.1529	$55.15	$55.15	$55.20
Purchase #3	$242.63	4.289%	$253.0364	$253.04	$253.05	$253.00
Purchase #4	$75.43	11.313%	$83.9634	$83.96	$83.95	$84.00
Purchase #5	$83.85	10.218%	$92.4178	$92.42	$92.40	$92.40
Purchase #6	$150.59	13.816%	$171.3955	$171.40	$171.40	$171.40
Purchase #7	$199.59	11.836%	$223.2135	$223.21	$223.20	$223.20
7 purchase totals =	$982.82		$1,079.3266	$1,079.33	$1,079.30	$1,079.30