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	$141.69	6.125%	$150.3685	$150.37	$150.35	$150.40
Purchase #2	$59.96	7.443%	$64.4228	$64.42	$64.40	$64.40
Purchase #3	$206.62	9.865%	$227.0031	$227.00	$227.00	$227.00
Purchase #4	$182.34	3.119%	$188.0272	$188.03	$188.05	$188.00
Purchase #5	$149.52	10.739%	$165.577	$165.58	$165.60	$165.60
Purchase #6	$25.85	7.301%	$27.7373	$27.74	$27.75	$27.70
Purchase #7	$174.58	8.613%	$189.6166	$189.62	$189.60	$189.60
7 purchase totals =	$940.56		$1,012.7525	$1,012.76	$1,012.75	$1,012.70