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	$198.98	7.632%	$214.1662	$214.17	$214.15	$214.20
Purchase #2	$137.51	4.767%	$144.0651	$144.07	$144.05	$144.10
Purchase #3	$132.27	6.458%	$140.812	$140.81	$140.80	$140.80
Purchase #4	$88.55	12.498%	$99.617	$99.62	$99.60	$99.60
Purchase #5	$238.48	11.475%	$265.8456	$265.85	$265.85	$265.80
Purchase #6	$113.98	11.483%	$127.0683	$127.07	$127.05	$127.10
Purchase #7	$248.53	12.174%	$278.786	$278.79	$278.80	$278.80
7 purchase totals =	$1,158.30		$1,270.3602	$1,270.38	$1,270.30	$1,270.40