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	$40.59	5.120%	$42.6682	$42.67	$42.65	$42.70
Purchase #2	$135.65	3.570%	$140.4927	$140.49	$140.50	$140.50
Purchase #3	$109.84	4.596%	$114.8882	$114.89	$114.90	$114.90
Purchase #4	$216.83	5.692%	$229.172	$229.17	$229.15	$229.20
Purchase #5	$150.71	12.662%	$169.7929	$169.79	$169.80	$169.80
Purchase #6	$166.80	5.326%	$175.6838	$175.68	$175.70	$175.70
Purchase #7	$123.76	12.684%	$139.4577	$139.46	$139.45	$139.50
7 purchase totals =	$944.18		$1,012.1555	$1,012.15	$1,012.15	$1,012.30