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	$250.52	10.508%	$276.8446	$276.84	$276.85	$276.80
Purchase #2	$217.82	13.514%	$247.2562	$247.26	$247.25	$247.30
Purchase #3	$32.41	7.439%	$34.821	$34.82	$34.80	$34.80
Purchase #4	$78.57	9.801%	$86.2706	$86.27	$86.25	$86.30
Purchase #5	$103.85	5.112%	$109.1588	$109.16	$109.15	$109.20
Purchase #6	$99.31	6.661%	$105.925	$105.93	$105.95	$105.90
Purchase #7	$197.78	9.114%	$215.8057	$215.81	$215.80	$215.80
7 purchase totals =	$980.26		$1,076.0819	$1,076.09	$1,076.05	$1,076.10