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	$68.89	3.380%	$71.2185	$71.22	$71.20	$71.20
Purchase #2	$107.46	12.430%	$120.8173	$120.82	$120.80	$120.80
Purchase #3	$68.65	4.848%	$71.9782	$71.98	$72.00	$72.00
Purchase #4	$231.34	5.471%	$243.9966	$244.00	$244.00	$244.00
Purchase #5	$168.66	13.785%	$191.9098	$191.91	$191.90	$191.90
Purchase #6	$215.45	9.386%	$235.6721	$235.67	$235.65	$235.70
Purchase #7	$112.66	12.114%	$126.3076	$126.31	$126.30	$126.30
7 purchase totals =	$973.11		$1,061.9001	$1,061.91	$1,061.85	$1,061.90