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	$161.89	11.327%	$180.2273	$180.23	$180.25	$180.20
Purchase #2	$82.27	11.626%	$91.8347	$91.83	$91.85	$91.80
Purchase #3	$179.40	9.104%	$195.7326	$195.73	$195.75	$195.70
Purchase #4	$213.95	5.601%	$225.9333	$225.93	$225.95	$225.90
Purchase #5	$245.31	13.434%	$278.2649	$278.26	$278.25	$278.30
Purchase #6	$136.80	5.643%	$144.5196	$144.52	$144.50	$144.50
Purchase #7	$54.29	4.172%	$56.555	$56.56	$56.55	$56.60
7 purchase totals =	$1,073.91		$1,173.0674	$1,173.06	$1,173.10	$1,173.00