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	$47.44	13.645%	$53.9132	$53.91	$53.90	$53.90
Purchase #2	$224.71	11.105%	$249.664	$249.66	$249.65	$249.70
Purchase #3	$161.78	5.261%	$170.2912	$170.29	$170.30	$170.30
Purchase #4	$61.65	13.864%	$70.1972	$70.20	$70.20	$70.20
Purchase #5	$167.34	12.617%	$188.4533	$188.45	$188.45	$188.50
Purchase #6	$235.61	6.781%	$251.5867	$251.59	$251.60	$251.60
Purchase #7	$120.81	5.302%	$127.2153	$127.22	$127.20	$127.20
7 purchase totals =	$1,019.34		$1,111.3209	$1,111.32	$1,111.30	$1,111.40