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	$221.30	11.869%	$247.5661	$247.57	$247.55	$247.60
Purchase #2	$215.63	11.575%	$240.5892	$240.59	$240.60	$240.60
Purchase #3	$118.33	12.479%	$133.0964	$133.10	$133.10	$133.10
Purchase #4	$233.32	13.528%	$264.8835	$264.88	$264.90	$264.90
Purchase #5	$94.53	4.612%	$98.8897	$98.89	$98.90	$98.90
Purchase #6	$66.26	12.313%	$74.4186	$74.42	$74.40	$74.40
Purchase #7	$120.44	13.794%	$137.0535	$137.05	$137.05	$137.10
7 purchase totals =	$1,069.81		$1,196.4970	$1,196.50	$1,196.50	$1,196.60