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	$60.60	8.504%	$65.7534	$65.75	$65.75	$65.80
Purchase #2	$161.86	6.379%	$172.185	$172.19	$172.20	$172.20
Purchase #3	$92.50	11.406%	$103.0506	$103.05	$103.05	$103.10
Purchase #4	$28.76	9.172%	$31.3979	$31.40	$31.40	$31.40
Purchase #5	$237.32	13.300%	$268.8836	$268.88	$268.90	$268.90
Purchase #6	$96.61	13.776%	$109.919	$109.92	$109.90	$109.90
Purchase #7	$176.59	5.611%	$186.4985	$186.50	$186.50	$186.50
7 purchase totals =	$854.24		$937.6880	$937.69	$937.70	$937.80