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	$186.65	4.150%	$194.396	$194.40	$194.40	$194.40
Purchase #2	$155.30	6.371%	$165.1942	$165.19	$165.20	$165.20
Purchase #3	$98.82	9.684%	$108.3897	$108.39	$108.40	$108.40
Purchase #4	$76.45	8.778%	$83.1608	$83.16	$83.15	$83.20
Purchase #5	$220.75	7.780%	$237.9244	$237.92	$237.90	$237.90
Purchase #6	$76.65	7.706%	$82.5566	$82.56	$82.55	$82.60
Purchase #7	$85.82	4.321%	$89.5283	$89.53	$89.55	$89.50
7 purchase totals =	$900.44		$961.1500	$961.15	$961.15	$961.20