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	$234.86	3.821%	$243.834	$243.83	$243.85	$243.80
Purchase #2	$97.46	8.417%	$105.6632	$105.66	$105.65	$105.70
Purchase #3	$223.89	9.243%	$244.5842	$244.58	$244.60	$244.60
Purchase #4	$147.72	8.164%	$159.7799	$159.78	$159.80	$159.80
Purchase #5	$141.41	6.535%	$150.6511	$150.65	$150.65	$150.70
Purchase #6	$186.98	4.835%	$196.0205	$196.02	$196.00	$196.00
Purchase #7	$245.68	4.338%	$256.3376	$256.34	$256.35	$256.30
7 purchase totals =	$1,278.00		$1,356.8705	$1,356.86	$1,356.90	$1,356.90