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	$133.96	6.787%	$143.0519	$143.05	$143.05	$143.10
Purchase #2	$167.52	12.209%	$187.9725	$187.97	$187.95	$188.00
Purchase #3	$240.90	9.863%	$264.66	$264.66	$264.65	$264.70
Purchase #4	$37.93	9.191%	$41.4161	$41.42	$41.40	$41.40
Purchase #5	$84.40	7.111%	$90.4017	$90.40	$90.40	$90.40
Purchase #6	$113.63	9.123%	$123.9965	$124.00	$124.00	$124.00
Purchase #7	$89.53	11.610%	$99.9244	$99.92	$99.90	$99.90
7 purchase totals =	$867.87		$951.4231	$951.42	$951.35	$951.50