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	$156.73	10.106%	$172.5691	$172.57	$172.55	$172.60
Purchase #2	$118.41	10.281%	$130.5837	$130.58	$130.60	$130.60
Purchase #3	$45.84	3.423%	$47.4091	$47.41	$47.40	$47.40
Purchase #4	$88.41	6.221%	$93.91	$93.91	$93.90	$93.90
Purchase #5	$115.87	6.516%	$123.4201	$123.42	$123.40	$123.40
Purchase #6	$17.93	3.693%	$18.5922	$18.59	$18.60	$18.60
Purchase #7	$95.59	5.728%	$101.0654	$101.07	$101.05	$101.10
7 purchase totals =	$638.78		$687.5496	$687.55	$687.50	$687.60