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	$148.47	13.793%	$168.9485	$168.95	$168.95	$168.90
Purchase #2	$128.90	3.289%	$133.1395	$133.14	$133.15	$133.10
Purchase #3	$187.53	12.519%	$211.0069	$211.01	$211.00	$211.00
Purchase #4	$120.30	12.457%	$135.2858	$135.29	$135.30	$135.30
Purchase #5	$37.36	13.696%	$42.4768	$42.48	$42.50	$42.50
Purchase #6	$195.44	13.866%	$222.5397	$222.54	$222.55	$222.50
Purchase #7	$16.45	8.768%	$17.8923	$17.89	$17.90	$17.90
7 purchase totals =	$834.45		$931.2895	$931.30	$931.35	$931.20