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	$229.55	6.444%	$244.3422	$244.34	$244.35	$244.30
Purchase #2	$245.47	10.608%	$271.5095	$271.51	$271.50	$271.50
Purchase #3	$201.80	5.223%	$212.34	$212.34	$212.35	$212.30
Purchase #4	$63.82	5.657%	$67.4303	$67.43	$67.45	$67.40
Purchase #5	$51.46	8.753%	$55.9643	$55.96	$55.95	$56.00
Purchase #6	$48.43	13.106%	$54.7772	$54.78	$54.80	$54.80
Purchase #7	$232.84	4.740%	$243.8766	$243.88	$243.90	$243.90
7 purchase totals =	$1,073.37		$1,150.2401	$1,150.24	$1,150.30	$1,150.20