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	$206.33	3.568%	$213.6919	$213.69	$213.70	$213.70
Purchase #2	$83.79	8.494%	$90.9071	$90.91	$90.90	$90.90
Purchase #3	$229.95	13.755%	$261.5796	$261.58	$261.60	$261.60
Purchase #4	$121.78	5.228%	$128.1467	$128.15	$128.15	$128.10
Purchase #5	$78.47	9.130%	$85.6343	$85.63	$85.65	$85.60
Purchase #6	$109.32	8.357%	$118.4559	$118.46	$118.45	$118.50
Purchase #7	$218.96	11.681%	$244.5367	$244.54	$244.55	$244.50
7 purchase totals =	$1,048.60		$1,142.9522	$1,142.96	$1,143.00	$1,142.90