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	$144.47	13.678%	$164.2306	$164.23	$164.25	$164.20
Purchase #2	$119.74	7.147%	$128.2978	$128.30	$128.30	$128.30
Purchase #3	$127.85	13.687%	$145.3488	$145.35	$145.35	$145.30
Purchase #4	$77.60	6.516%	$82.6564	$82.66	$82.65	$82.70
Purchase #5	$247.77	6.714%	$264.4053	$264.41	$264.40	$264.40
Purchase #6	$112.69	5.461%	$118.844	$118.84	$118.85	$118.80
Purchase #7	$72.57	13.223%	$82.1659	$82.17	$82.15	$82.20
7 purchase totals =	$902.69		$985.9488	$985.96	$985.95	$985.90