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	$50.96	3.857%	$52.9255	$52.93	$52.95	$52.90
Purchase #2	$147.35	3.414%	$152.3805	$152.38	$152.40	$152.40
Purchase #3	$50.43	6.873%	$53.8961	$53.90	$53.90	$53.90
Purchase #4	$243.48	12.341%	$273.5279	$273.53	$273.55	$273.50
Purchase #5	$181.53	9.787%	$199.2963	$199.30	$199.30	$199.30
Purchase #6	$144.56	10.243%	$159.3673	$159.37	$159.35	$159.40
Purchase #7	$66.88	8.687%	$72.6899	$72.69	$72.70	$72.70
7 purchase totals =	$885.19		$964.0835	$964.10	$964.15	$964.10