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	$210.33	6.530%	$224.0645	$224.06	$224.05	$224.10
Purchase #2	$39.36	5.831%	$41.6551	$41.66	$41.65	$41.70
Purchase #3	$111.80	7.231%	$119.8843	$119.88	$119.90	$119.90
Purchase #4	$233.44	13.311%	$264.5132	$264.51	$264.50	$264.50
Purchase #5	$40.94	3.622%	$42.4228	$42.42	$42.40	$42.40
Purchase #6	$141.97	5.545%	$149.8422	$149.84	$149.85	$149.80
Purchase #7	$188.72	5.375%	$198.8637	$198.86	$198.85	$198.90
7 purchase totals =	$966.56		$1,041.2458	$1,041.23	$1,041.20	$1,041.30