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	$56.71	9.155%	$61.9018	$61.90	$61.90	$61.90
Purchase #2	$247.64	13.285%	$280.539	$280.54	$280.55	$280.50
Purchase #3	$187.75	4.580%	$196.349	$196.35	$196.35	$196.30
Purchase #4	$127.48	9.873%	$140.0661	$140.07	$140.05	$140.10
Purchase #5	$90.41	10.217%	$99.6472	$99.65	$99.65	$99.60
Purchase #6	$196.80	3.528%	$203.7431	$203.74	$203.75	$203.70
Purchase #7	$178.68	11.864%	$199.8786	$199.88	$199.90	$199.90
7 purchase totals =	$1,085.47		$1,182.1248	$1,182.13	$1,182.15	$1,182.00