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	$42.61	13.774%	$48.4791	$48.48	$48.50	$48.50
Purchase #2	$211.82	13.558%	$240.5386	$240.54	$240.55	$240.50
Purchase #3	$156.70	10.522%	$173.188	$173.19	$173.20	$173.20
Purchase #4	$171.65	10.736%	$190.0783	$190.08	$190.10	$190.10
Purchase #5	$209.66	9.501%	$229.5798	$229.58	$229.60	$229.60
Purchase #6	$30.66	6.369%	$32.6127	$32.61	$32.60	$32.60
Purchase #7	$96.63	3.110%	$99.6352	$99.64	$99.65	$99.60
7 purchase totals =	$919.73		$1,014.1117	$1,014.12	$1,014.20	$1,014.10