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	$54.97	8.208%	$59.4819	$59.48	$59.50	$59.50
Purchase #2	$124.51	10.565%	$137.6645	$137.66	$137.65	$137.70
Purchase #3	$229.55	10.670%	$254.043	$254.04	$254.05	$254.00
Purchase #4	$148.49	12.501%	$167.0527	$167.05	$167.05	$167.10
Purchase #5	$210.41	8.638%	$228.5852	$228.59	$228.60	$228.60
Purchase #6	$234.25	12.156%	$262.7254	$262.73	$262.75	$262.70
Purchase #7	$80.98	11.763%	$90.5057	$90.51	$90.50	$90.50
7 purchase totals =	$1,083.16		$1,200.0584	$1,200.06	$1,200.10	$1,200.10