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	$130.68	9.356%	$142.9064	$142.91	$142.90	$142.90
Purchase #2	$218.72	11.711%	$244.3343	$244.33	$244.35	$244.30
Purchase #3	$127.26	11.240%	$141.564	$141.56	$141.55	$141.60
Purchase #4	$55.36	7.326%	$59.4157	$59.42	$59.40	$59.40
Purchase #5	$246.83	10.429%	$272.5719	$272.57	$272.55	$272.60
Purchase #6	$30.92	6.520%	$32.936	$32.94	$32.95	$32.90
Purchase #7	$190.92	5.344%	$201.1228	$201.12	$201.10	$201.10
7 purchase totals =	$1,000.69		$1,094.8511	$1,094.85	$1,094.80	$1,094.80