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	$123.25	3.233%	$127.2347	$127.23	$127.25	$127.20
Purchase #2	$163.78	4.862%	$171.743	$171.74	$171.75	$171.70
Purchase #3	$184.56	8.102%	$199.5131	$199.51	$199.50	$199.50
Purchase #4	$247.96	8.646%	$269.3986	$269.40	$269.40	$269.40
Purchase #5	$208.41	6.816%	$222.6152	$222.62	$222.60	$222.60
Purchase #6	$231.34	12.165%	$259.4825	$259.48	$259.50	$259.50
Purchase #7	$102.47	4.310%	$106.8865	$106.89	$106.90	$106.90
7 purchase totals =	$1,261.77		$1,356.8736	$1,356.87	$1,356.90	$1,356.80