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	$203.53	12.843%	$229.6694	$229.67	$229.65	$229.70
Purchase #2	$64.54	4.474%	$67.4275	$67.43	$67.45	$67.40
Purchase #3	$35.81	13.740%	$40.7303	$40.73	$40.75	$40.70
Purchase #4	$218.31	5.176%	$229.6097	$229.61	$229.60	$229.60
Purchase #5	$246.46	3.308%	$254.6129	$254.61	$254.60	$254.60
Purchase #6	$239.44	8.500%	$259.7924	$259.79	$259.80	$259.80
Purchase #7	$134.73	4.351%	$140.5921	$140.59	$140.60	$140.60
7 purchase totals =	$1,142.82		$1,222.4343	$1,222.43	$1,222.45	$1,222.40