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	$128.77	9.764%	$141.3431	$141.34	$141.35	$141.30
Purchase #2	$72.25	8.155%	$78.142	$78.14	$78.15	$78.10
Purchase #3	$187.34	3.829%	$194.5132	$194.51	$194.50	$194.50
Purchase #4	$216.42	11.707%	$241.7563	$241.76	$241.75	$241.80
Purchase #5	$198.89	11.705%	$222.1701	$222.17	$222.15	$222.20
Purchase #6	$213.97	8.696%	$232.5768	$232.58	$232.60	$232.60
Purchase #7	$144.51	5.308%	$152.1806	$152.18	$152.20	$152.20
7 purchase totals =	$1,162.15		$1,262.6821	$1,262.68	$1,262.70	$1,262.70