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	$146.59	12.123%	$164.3611	$164.36	$164.35	$164.40
Purchase #2	$19.56	11.740%	$21.8563	$21.86	$21.85	$21.90
Purchase #3	$146.25	12.627%	$164.717	$164.72	$164.70	$164.70
Purchase #4	$39.87	8.367%	$43.2059	$43.21	$43.20	$43.20
Purchase #5	$118.62	12.443%	$133.3799	$133.38	$133.40	$133.40
Purchase #6	$50.39	6.859%	$53.8463	$53.85	$53.85	$53.80
Purchase #7	$38.73	6.350%	$41.1894	$41.19	$41.20	$41.20
7 purchase totals =	$560.01		$622.5559	$622.57	$622.55	$622.60