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	$144.89	7.749%	$156.1175	$156.12	$156.10	$156.10
Purchase #2	$162.74	3.145%	$167.8582	$167.86	$167.85	$167.90
Purchase #3	$87.91	10.219%	$96.8935	$96.89	$96.90	$96.90
Purchase #4	$105.95	7.306%	$113.6907	$113.69	$113.70	$113.70
Purchase #5	$95.72	4.376%	$99.9087	$99.91	$99.90	$99.90
Purchase #6	$188.50	10.657%	$208.5884	$208.59	$208.60	$208.60
Purchase #7	$197.97	12.551%	$222.8172	$222.82	$222.80	$222.80
7 purchase totals =	$983.68		$1,065.8742	$1,065.88	$1,065.85	$1,065.90