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	$147.26	10.259%	$162.3674	$162.37	$162.35	$162.40
Purchase #2	$45.50	12.350%	$51.1193	$51.12	$51.10	$51.10
Purchase #3	$223.61	8.281%	$242.1271	$242.13	$242.15	$242.10
Purchase #4	$102.85	8.867%	$111.9697	$111.97	$111.95	$112.00
Purchase #5	$241.42	13.215%	$273.3237	$273.32	$273.30	$273.30
Purchase #6	$43.41	9.153%	$47.3833	$47.38	$47.40	$47.40
Purchase #7	$155.43	4.636%	$162.6357	$162.64	$162.65	$162.60
7 purchase totals =	$959.48		$1,050.9262	$1,050.93	$1,050.90	$1,050.90