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	$32.55	10.474%	$35.9593	$35.96	$35.95	$36.00
Purchase #2	$84.53	13.581%	$96.01	$96.01	$96.00	$96.00
Purchase #3	$161.48	11.815%	$180.5589	$180.56	$180.55	$180.60
Purchase #4	$184.86	6.520%	$196.9129	$196.91	$196.90	$196.90
Purchase #5	$77.30	11.523%	$86.2073	$86.21	$86.20	$86.20
Purchase #6	$31.96	11.315%	$35.5763	$35.58	$35.60	$35.60
Purchase #7	$159.68	7.851%	$172.2165	$172.22	$172.20	$172.20
7 purchase totals =	$732.36		$803.4412	$803.45	$803.40	$803.50