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	$108.51	3.323%	$112.1158	$112.12	$112.10	$112.10
Purchase #2	$155.94	6.131%	$165.5007	$165.50	$165.50	$165.50
Purchase #3	$56.79	3.123%	$58.5636	$58.56	$58.55	$58.60
Purchase #4	$136.86	9.465%	$149.8138	$149.81	$149.80	$149.80
Purchase #5	$98.94	12.614%	$111.4203	$111.42	$111.40	$111.40
Purchase #6	$50.80	12.112%	$56.9529	$56.95	$56.95	$57.00
Purchase #7	$85.93	4.396%	$89.7075	$89.71	$89.70	$89.70
7 purchase totals =	$693.77		$744.0746	$744.07	$744.00	$744.10