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	$168.48	3.490%	$174.36	$174.36	$174.35	$174.40
Purchase #2	$84.42	6.446%	$89.8617	$89.86	$89.85	$89.90
Purchase #3	$155.29	6.781%	$165.8202	$165.82	$165.80	$165.80
Purchase #4	$142.45	13.584%	$161.8004	$161.80	$161.80	$161.80
Purchase #5	$64.40	12.738%	$72.6033	$72.60	$72.60	$72.60
Purchase #6	$217.38	8.121%	$235.0334	$235.03	$235.05	$235.00
Purchase #7	$217.78	6.657%	$232.2776	$232.28	$232.30	$232.30
7 purchase totals =	$1,050.20		$1,131.7566	$1,131.75	$1,131.75	$1,131.80