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	$178.47	3.290%	$184.3417	$184.34	$184.35	$184.30
Purchase #2	$25.25	8.210%	$27.323	$27.32	$27.30	$27.30
Purchase #3	$126.65	12.433%	$142.3964	$142.40	$142.40	$142.40
Purchase #4	$223.62	11.837%	$250.0899	$250.09	$250.10	$250.10
Purchase #5	$142.62	12.108%	$159.8884	$159.89	$159.90	$159.90
Purchase #6	$96.29	3.853%	$100.0001	$100.00	$100.00	$100.00
Purchase #7	$171.30	11.792%	$191.4997	$191.50	$191.50	$191.50
7 purchase totals =	$964.20		$1,055.5392	$1,055.54	$1,055.55	$1,055.50