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	$199.71	11.773%	$223.2219	$223.22	$223.20	$223.20
Purchase #2	$77.98	4.769%	$81.6989	$81.70	$81.70	$81.70
Purchase #3	$220.84	7.300%	$236.9613	$236.96	$236.95	$237.00
Purchase #4	$176.73	12.541%	$198.8937	$198.89	$198.90	$198.90
Purchase #5	$175.64	5.736%	$185.7147	$185.71	$185.70	$185.70
Purchase #6	$50.86	3.379%	$52.5786	$52.58	$52.60	$52.60
Purchase #7	$111.77	13.257%	$126.5873	$126.59	$126.60	$126.60
7 purchase totals =	$1,013.53		$1,105.6564	$1,105.65	$1,105.65	$1,105.70