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	$97.49	6.864%	$104.1817	$104.18	$104.20	$104.20
Purchase #2	$33.78	10.838%	$37.4411	$37.44	$37.45	$37.40
Purchase #3	$24.43	13.700%	$27.7769	$27.78	$27.80	$27.80
Purchase #4	$233.54	9.327%	$255.3223	$255.32	$255.30	$255.30
Purchase #5	$99.91	6.637%	$106.541	$106.54	$106.55	$106.50
Purchase #6	$161.96	3.251%	$167.2253	$167.23	$167.25	$167.20
Purchase #7	$22.41	10.626%	$24.7913	$24.79	$24.80	$24.80
7 purchase totals =	$673.52		$723.2796	$723.28	$723.35	$723.20