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	$58.82	4.688%	$61.5775	$61.58	$61.60	$61.60
Purchase #2	$232.29	3.818%	$241.1588	$241.16	$241.15	$241.20
Purchase #3	$42.60	11.613%	$47.5471	$47.55	$47.55	$47.50
Purchase #4	$141.38	5.330%	$148.9156	$148.92	$148.90	$148.90
Purchase #5	$55.35	11.358%	$61.6367	$61.64	$61.65	$61.60
Purchase #6	$244.38	6.320%	$259.8248	$259.82	$259.80	$259.80
Purchase #7	$136.98	13.394%	$155.3271	$155.33	$155.35	$155.30
7 purchase totals =	$911.80		$975.9876	$976.00	$976.00	$975.90