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	$58.77	10.234%	$64.7845	$64.78	$64.80	$64.80
Purchase #2	$166.95	10.765%	$184.9222	$184.92	$184.90	$184.90
Purchase #3	$246.89	3.295%	$255.025	$255.03	$255.05	$255.00
Purchase #4	$51.64	13.872%	$58.8035	$58.80	$58.80	$58.80
Purchase #5	$74.89	4.192%	$78.0294	$78.03	$78.05	$78.00
Purchase #6	$53.32	5.567%	$56.2883	$56.29	$56.30	$56.30
Purchase #7	$158.40	11.421%	$176.4909	$176.49	$176.50	$176.50
7 purchase totals =	$810.86		$874.3438	$874.34	$874.40	$874.30