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	$100.40	4.228%	$104.6449	$104.64	$104.65	$104.60
Purchase #2	$76.56	7.764%	$82.5041	$82.50	$82.50	$82.50
Purchase #3	$162.28	6.697%	$173.1479	$173.15	$173.15	$173.10
Purchase #4	$172.31	9.319%	$188.3676	$188.37	$188.35	$188.40
Purchase #5	$191.44	12.468%	$215.3087	$215.31	$215.30	$215.30
Purchase #6	$206.85	6.283%	$219.8464	$219.85	$219.85	$219.80
Purchase #7	$141.60	10.475%	$156.4326	$156.43	$156.45	$156.40
7 purchase totals =	$1,051.44		$1,140.2522	$1,140.25	$1,140.25	$1,140.10