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	$130.89	4.357%	$136.5929	$136.59	$136.60	$136.60
Purchase #2	$188.70	4.177%	$196.582	$196.58	$196.60	$196.60
Purchase #3	$88.65	3.103%	$91.4008	$91.40	$91.40	$91.40
Purchase #4	$58.84	4.465%	$61.4672	$61.47	$61.45	$61.50
Purchase #5	$191.41	7.632%	$206.0184	$206.02	$206.00	$206.00
Purchase #6	$116.72	6.527%	$124.3383	$124.34	$124.35	$124.30
Purchase #7	$9.52	8.275%	$10.3078	$10.31	$10.30	$10.30
7 purchase totals =	$784.73		$826.7074	$826.71	$826.70	$826.70