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	$113.53	4.578%	$118.7274	$118.73	$118.75	$118.70
Purchase #2	$68.60	3.111%	$70.7341	$70.73	$70.75	$70.70
Purchase #3	$219.92	11.498%	$245.2064	$245.21	$245.20	$245.20
Purchase #4	$128.55	12.298%	$144.3591	$144.36	$144.35	$144.40
Purchase #5	$92.42	7.767%	$99.5983	$99.60	$99.60	$99.60
Purchase #6	$235.73	11.304%	$262.3769	$262.38	$262.40	$262.40
Purchase #7	$211.47	9.411%	$231.3714	$231.37	$231.35	$231.40
7 purchase totals =	$1,070.22		$1,172.3736	$1,172.38	$1,172.40	$1,172.40