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	$136.85	11.130%	$152.0814	$152.08	$152.10	$152.10
Purchase #2	$90.42	6.770%	$96.5414	$96.54	$96.55	$96.50
Purchase #3	$86.90	9.644%	$95.2806	$95.28	$95.30	$95.30
Purchase #4	$225.80	10.721%	$250.008	$250.01	$250.00	$250.00
Purchase #5	$116.55	3.683%	$120.8425	$120.84	$120.85	$120.80
Purchase #6	$31.73	13.322%	$35.9571	$35.96	$35.95	$36.00
Purchase #7	$234.53	11.599%	$261.7331	$261.73	$261.75	$261.70
7 purchase totals =	$922.78		$1,012.4441	$1,012.44	$1,012.50	$1,012.40