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	$113.42	12.396%	$127.4795	$127.48	$127.50	$127.50
Purchase #2	$137.28	13.151%	$155.3337	$155.33	$155.35	$155.30
Purchase #3	$67.98	4.140%	$70.7944	$70.79	$70.80	$70.80
Purchase #4	$32.79	8.507%	$35.5794	$35.58	$35.60	$35.60
Purchase #5	$209.96	9.367%	$229.627	$229.63	$229.65	$229.60
Purchase #6	$225.85	12.425%	$253.9119	$253.91	$253.90	$253.90
Purchase #7	$126.33	12.270%	$141.8307	$141.83	$141.85	$141.80
7 purchase totals =	$913.61		$1,014.5566	$1,014.55	$1,014.65	$1,014.50