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	$135.82	9.424%	$148.6197	$148.62	$148.60	$148.60
Purchase #2	$46.36	13.862%	$52.7864	$52.79	$52.80	$52.80
Purchase #3	$242.29	11.816%	$270.919	$270.92	$270.90	$270.90
Purchase #4	$99.82	11.631%	$111.4301	$111.43	$111.45	$111.40
Purchase #5	$30.56	8.123%	$33.0424	$33.04	$33.05	$33.00
Purchase #6	$163.75	11.796%	$183.066	$183.07	$183.05	$183.10
Purchase #7	$50.82	7.597%	$54.6808	$54.68	$54.70	$54.70
7 purchase totals =	$769.42		$854.5444	$854.55	$854.55	$854.50