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	$136.47	11.552%	$152.235	$152.24	$152.25	$152.20
Purchase #2	$131.64	8.180%	$142.4082	$142.41	$142.40	$142.40
Purchase #3	$213.51	10.552%	$236.0396	$236.04	$236.05	$236.00
Purchase #4	$244.95	11.801%	$273.8565	$273.86	$273.85	$273.90
Purchase #5	$56.69	4.344%	$59.1526	$59.15	$59.15	$59.20
Purchase #6	$246.64	13.221%	$279.2483	$279.25	$279.25	$279.20
Purchase #7	$98.33	7.621%	$105.8237	$105.82	$105.80	$105.80
7 purchase totals =	$1,128.23		$1,248.7639	$1,248.77	$1,248.75	$1,248.70