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	$63.75	3.715%	$66.1183	$66.12	$66.10	$66.10
Purchase #2	$168.31	12.210%	$188.8607	$188.86	$188.85	$188.90
Purchase #3	$69.83	3.331%	$72.156	$72.16	$72.15	$72.20
Purchase #4	$141.89	8.241%	$153.5832	$153.58	$153.60	$153.60
Purchase #5	$178.79	3.753%	$185.5	$185.50	$185.50	$185.50
Purchase #6	$49.65	11.667%	$55.4427	$55.44	$55.45	$55.40
Purchase #7	$173.55	9.396%	$189.8568	$189.86	$189.85	$189.90
7 purchase totals =	$845.77		$911.5177	$911.52	$911.50	$911.60