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	$207.77	6.717%	$221.7259	$221.73	$221.75	$221.70
Purchase #2	$89.80	10.508%	$99.2362	$99.24	$99.25	$99.20
Purchase #3	$220.82	10.560%	$244.1386	$244.14	$244.15	$244.10
Purchase #4	$64.34	13.799%	$73.2183	$73.22	$73.20	$73.20
Purchase #5	$87.73	3.480%	$90.783	$90.78	$90.80	$90.80
Purchase #6	$131.26	6.701%	$140.0557	$140.06	$140.05	$140.10
Purchase #7	$64.74	13.399%	$73.4145	$73.41	$73.40	$73.40
7 purchase totals =	$866.46		$942.5722	$942.58	$942.60	$942.50