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	$212.53	10.590%	$235.0369	$235.04	$235.05	$235.00
Purchase #2	$109.66	12.636%	$123.5166	$123.52	$123.50	$123.50
Purchase #3	$170.46	5.133%	$179.2097	$179.21	$179.20	$179.20
Purchase #4	$79.27	4.168%	$82.574	$82.57	$82.55	$82.60
Purchase #5	$125.81	13.512%	$142.8094	$142.81	$142.80	$142.80
Purchase #6	$216.42	11.159%	$240.5703	$240.57	$240.55	$240.60
Purchase #7	$197.29	5.671%	$208.4783	$208.48	$208.50	$208.50
7 purchase totals =	$1,111.44		$1,212.1952	$1,212.20	$1,212.15	$1,212.20