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	$33.81	5.593%	$35.701	$35.70	$35.70	$35.70
Purchase #2	$56.89	7.459%	$61.1334	$61.13	$61.15	$61.10
Purchase #3	$239.31	10.694%	$264.9018	$264.90	$264.90	$264.90
Purchase #4	$50.68	9.550%	$55.5199	$55.52	$55.50	$55.50
Purchase #5	$145.25	12.255%	$163.0504	$163.05	$163.05	$163.10
Purchase #6	$144.86	5.225%	$152.4289	$152.43	$152.45	$152.40
Purchase #7	$115.33	6.683%	$123.0375	$123.04	$123.05	$123.00
7 purchase totals =	$786.13		$855.7729	$855.77	$855.80	$855.70