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	$98.42	5.487%	$103.8203	$103.82	$103.80	$103.80
Purchase #2	$97.25	12.869%	$109.7651	$109.77	$109.75	$109.80
Purchase #3	$95.30	5.478%	$100.5205	$100.52	$100.50	$100.50
Purchase #4	$61.77	7.341%	$66.3045	$66.30	$66.30	$66.30
Purchase #5	$239.48	9.410%	$262.0151	$262.02	$262.00	$262.00
Purchase #6	$72.79	3.729%	$75.5043	$75.50	$75.50	$75.50
Purchase #7	$156.76	12.504%	$176.3613	$176.36	$176.35	$176.40
7 purchase totals =	$821.77		$894.2911	$894.29	$894.20	$894.30