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	$153.84	12.228%	$172.6516	$172.65	$172.65	$172.70
Purchase #2	$125.53	4.443%	$131.1073	$131.11	$131.10	$131.10
Purchase #3	$178.60	3.592%	$185.0153	$185.02	$185.00	$185.00
Purchase #4	$14.80	4.386%	$15.4491	$15.45	$15.45	$15.40
Purchase #5	$139.52	3.275%	$144.0893	$144.09	$144.10	$144.10
Purchase #6	$57.76	4.179%	$60.1738	$60.17	$60.15	$60.20
Purchase #7	$78.47	7.582%	$84.4196	$84.42	$84.40	$84.40
7 purchase totals =	$748.52		$792.9060	$792.91	$792.85	$792.90