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	$120.94	7.104%	$129.5316	$129.53	$129.55	$129.50
Purchase #2	$37.65	13.729%	$42.819	$42.82	$42.80	$42.80
Purchase #3	$217.68	3.782%	$225.9127	$225.91	$225.90	$225.90
Purchase #4	$167.90	3.446%	$173.6858	$173.69	$173.70	$173.70
Purchase #5	$161.75	6.297%	$171.9354	$171.94	$171.95	$171.90
Purchase #6	$119.38	3.162%	$123.1548	$123.15	$123.15	$123.20
Purchase #7	$230.73	6.461%	$245.6375	$245.64	$245.65	$245.60
7 purchase totals =	$1,056.03		$1,112.6768	$1,112.68	$1,112.70	$1,112.60