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	$127.75	5.170%	$134.3547	$134.35	$134.35	$134.40
Purchase #2	$222.40	9.388%	$243.2789	$243.28	$243.30	$243.30
Purchase #3	$40.56	4.546%	$42.4039	$42.40	$42.40	$42.40
Purchase #4	$88.47	3.193%	$91.2948	$91.29	$91.30	$91.30
Purchase #5	$72.65	13.678%	$82.5871	$82.59	$82.60	$82.60
Purchase #6	$97.81	9.361%	$106.966	$106.97	$106.95	$107.00
Purchase #7	$25.74	12.244%	$28.8916	$28.89	$28.90	$28.90
7 purchase totals =	$675.38		$729.7770	$729.77	$729.80	$729.90