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	$225.48	3.804%	$234.0573	$234.06	$234.05	$234.10
Purchase #2	$36.97	3.222%	$38.1612	$38.16	$38.15	$38.20
Purchase #3	$182.54	3.294%	$188.5529	$188.55	$188.55	$188.60
Purchase #4	$127.31	9.492%	$139.3943	$139.39	$139.40	$139.40
Purchase #5	$150.66	13.655%	$171.2326	$171.23	$171.25	$171.20
Purchase #6	$113.41	8.767%	$123.3527	$123.35	$123.35	$123.40
Purchase #7	$132.52	10.803%	$146.8361	$146.84	$146.85	$146.80
7 purchase totals =	$968.89		$1,041.5871	$1,041.58	$1,041.60	$1,041.70