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	$233.82	8.257%	$253.1265	$253.13	$253.15	$253.10
Purchase #2	$89.56	5.417%	$94.4115	$94.41	$94.40	$94.40
Purchase #3	$213.50	13.725%	$242.8029	$242.80	$242.80	$242.80
Purchase #4	$142.90	3.731%	$148.2316	$148.23	$148.25	$148.20
Purchase #5	$90.77	5.607%	$95.8595	$95.86	$95.85	$95.90
Purchase #6	$158.58	5.525%	$167.3415	$167.34	$167.35	$167.30
Purchase #7	$59.37	13.802%	$67.5642	$67.56	$67.55	$67.60
7 purchase totals =	$988.50		$1,069.3377	$1,069.33	$1,069.35	$1,069.30