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	$119.25	13.434%	$135.27	$135.27	$135.25	$135.30
Purchase #2	$196.43	4.640%	$205.5444	$205.54	$205.55	$205.50
Purchase #3	$111.72	5.550%	$117.9205	$117.92	$117.90	$117.90
Purchase #4	$203.64	4.287%	$212.37	$212.37	$212.35	$212.40
Purchase #5	$37.29	4.744%	$39.059	$39.06	$39.05	$39.10
Purchase #6	$211.80	11.196%	$235.5131	$235.51	$235.50	$235.50
Purchase #7	$123.39	6.498%	$131.4079	$131.41	$131.40	$131.40
7 purchase totals =	$1,003.52		$1,077.0849	$1,077.08	$1,077.00	$1,077.10