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	$229.84	3.368%	$237.581	$237.58	$237.60	$237.60
Purchase #2	$114.57	8.123%	$123.8765	$123.88	$123.90	$123.90
Purchase #3	$58.43	13.218%	$66.1533	$66.15	$66.15	$66.20
Purchase #4	$232.77	6.145%	$247.0737	$247.07	$247.05	$247.10
Purchase #5	$172.54	10.386%	$190.46	$190.46	$190.45	$190.50
Purchase #6	$198.73	11.234%	$221.0553	$221.06	$221.05	$221.10
Purchase #7	$76.84	8.333%	$83.2431	$83.24	$83.25	$83.20
7 purchase totals =	$1,083.72		$1,169.4429	$1,169.44	$1,169.45	$1,169.60