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	$172.59	4.135%	$179.7266	$179.73	$179.75	$179.70
Purchase #2	$196.85	6.595%	$209.8323	$209.83	$209.85	$209.80
Purchase #3	$164.53	8.582%	$178.65	$178.65	$178.65	$178.70
Purchase #4	$50.70	12.346%	$56.9594	$56.96	$56.95	$57.00
Purchase #5	$155.80	5.634%	$164.5778	$164.58	$164.60	$164.60
Purchase #6	$39.83	10.752%	$44.1125	$44.11	$44.10	$44.10
Purchase #7	$219.55	3.526%	$227.2913	$227.29	$227.30	$227.30
7 purchase totals =	$999.85		$1,061.1499	$1,061.15	$1,061.20	$1,061.20