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	$82.79	13.620%	$94.066	$94.07	$94.05	$94.10
Purchase #2	$90.93	13.607%	$103.3028	$103.30	$103.30	$103.30
Purchase #3	$87.80	9.538%	$96.1744	$96.17	$96.15	$96.20
Purchase #4	$41.67	10.430%	$46.0162	$46.02	$46.00	$46.00
Purchase #5	$33.55	6.829%	$35.8411	$35.84	$35.85	$35.80
Purchase #6	$54.79	9.197%	$59.829	$59.83	$59.85	$59.80
Purchase #7	$218.60	6.356%	$232.4942	$232.49	$232.50	$232.50
7 purchase totals =	$610.13		$667.7237	$667.72	$667.70	$667.70