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	$121.46	8.555%	$131.8509	$131.85	$131.85	$131.90
Purchase #2	$120.61	4.128%	$125.5888	$125.59	$125.60	$125.60
Purchase #3	$171.92	3.197%	$177.4163	$177.42	$177.40	$177.40
Purchase #4	$197.78	8.859%	$215.3013	$215.30	$215.30	$215.30
Purchase #5	$33.78	5.177%	$35.5288	$35.53	$35.55	$35.50
Purchase #6	$80.48	13.760%	$91.554	$91.55	$91.55	$91.60
Purchase #7	$41.67	3.791%	$43.2497	$43.25	$43.25	$43.20
7 purchase totals =	$767.70		$820.4898	$820.49	$820.50	$820.50