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	$236.31	3.341%	$244.2051	$244.21	$244.20	$244.20
Purchase #2	$82.62	8.615%	$89.7377	$89.74	$89.75	$89.70
Purchase #3	$140.68	11.116%	$156.318	$156.32	$156.30	$156.30
Purchase #4	$94.97	4.358%	$99.1088	$99.11	$99.10	$99.10
Purchase #5	$156.32	8.699%	$169.9183	$169.92	$169.90	$169.90
Purchase #6	$222.70	4.569%	$232.8752	$232.88	$232.90	$232.90
Purchase #7	$59.62	4.710%	$62.4281	$62.43	$62.45	$62.40
7 purchase totals =	$993.22		$1,054.5912	$1,054.61	$1,054.60	$1,054.50