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	$136.92	3.464%	$141.6629	$141.66	$141.65	$141.70
Purchase #2	$112.28	11.735%	$125.4561	$125.46	$125.45	$125.50
Purchase #3	$188.35	12.143%	$211.2213	$211.22	$211.20	$211.20
Purchase #4	$128.49	11.681%	$143.4989	$143.50	$143.50	$143.50
Purchase #5	$247.43	10.388%	$273.133	$273.13	$273.15	$273.10
Purchase #6	$165.50	5.229%	$174.154	$174.15	$174.15	$174.20
Purchase #7	$93.34	6.845%	$99.7291	$99.73	$99.75	$99.70
7 purchase totals =	$1,072.31		$1,168.8553	$1,168.85	$1,168.85	$1,168.90