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	$96.93	13.429%	$109.9467	$109.95	$109.95	$109.90
Purchase #2	$188.52	3.113%	$194.3886	$194.39	$194.40	$194.40
Purchase #3	$64.59	9.121%	$70.4813	$70.48	$70.50	$70.50
Purchase #4	$96.95	3.518%	$100.3607	$100.36	$100.35	$100.40
Purchase #5	$208.78	11.152%	$232.0631	$232.06	$232.05	$232.10
Purchase #6	$62.89	6.317%	$66.8628	$66.86	$66.85	$66.90
Purchase #7	$206.53	7.795%	$222.629	$222.63	$222.65	$222.60
7 purchase totals =	$925.19		$996.7322	$996.73	$996.75	$996.80