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	$63.61	11.659%	$71.0263	$71.03	$71.05	$71.00
Purchase #2	$52.80	7.266%	$56.6364	$56.64	$56.65	$56.60
Purchase #3	$118.56	11.439%	$132.1221	$132.12	$132.10	$132.10
Purchase #4	$60.77	8.123%	$65.7063	$65.71	$65.70	$65.70
Purchase #5	$185.86	5.481%	$196.047	$196.05	$196.05	$196.00
Purchase #6	$211.37	10.631%	$233.8407	$233.84	$233.85	$233.80
Purchase #7	$206.62	11.224%	$229.811	$229.81	$229.80	$229.80
7 purchase totals =	$899.59		$985.1898	$985.20	$985.20	$985.00