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	$188.80	10.730%	$209.0582	$209.06	$209.05	$209.10
Purchase #2	$246.92	3.206%	$254.8363	$254.84	$254.85	$254.80
Purchase #3	$29.76	9.732%	$32.6562	$32.66	$32.65	$32.70
Purchase #4	$113.56	4.421%	$118.5805	$118.58	$118.60	$118.60
Purchase #5	$216.48	4.346%	$225.8882	$225.89	$225.90	$225.90
Purchase #6	$44.33	9.664%	$48.6141	$48.61	$48.60	$48.60
Purchase #7	$170.87	11.411%	$190.368	$190.37	$190.35	$190.40
7 purchase totals =	$1,010.72		$1,080.0015	$1,080.01	$1,080.00	$1,080.10