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	$71.64	6.158%	$76.0516	$76.05	$76.05	$76.10
Purchase #2	$226.72	7.859%	$244.5379	$244.54	$244.55	$244.50
Purchase #3	$17.56	4.311%	$18.317	$18.32	$18.30	$18.30
Purchase #4	$134.86	11.404%	$150.2394	$150.24	$150.25	$150.20
Purchase #5	$249.29	8.536%	$270.5694	$270.57	$270.55	$270.60
Purchase #6	$77.41	7.854%	$83.4898	$83.49	$83.50	$83.50
Purchase #7	$172.25	4.808%	$180.5318	$180.53	$180.55	$180.50
7 purchase totals =	$949.73		$1,023.7369	$1,023.74	$1,023.75	$1,023.70