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	$202.82	11.185%	$225.5054	$225.51	$225.50	$225.50
Purchase #2	$182.47	4.564%	$190.7979	$190.80	$190.80	$190.80
Purchase #3	$223.93	4.333%	$233.6329	$233.63	$233.65	$233.60
Purchase #4	$158.50	4.253%	$165.241	$165.24	$165.25	$165.20
Purchase #5	$171.61	6.242%	$182.3219	$182.32	$182.30	$182.30
Purchase #6	$11.36	9.212%	$12.4065	$12.41	$12.40	$12.40
Purchase #7	$79.63	10.222%	$87.7698	$87.77	$87.75	$87.80
7 purchase totals =	$1,030.32		$1,097.6754	$1,097.68	$1,097.65	$1,097.60