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	$112.78	9.845%	$123.8832	$123.88	$123.90	$123.90
Purchase #2	$42.41	12.167%	$47.57	$47.57	$47.55	$47.60
Purchase #3	$183.89	4.217%	$191.6446	$191.64	$191.65	$191.60
Purchase #4	$85.46	11.412%	$95.2127	$95.21	$95.20	$95.20
Purchase #5	$171.38	7.849%	$184.8316	$184.83	$184.85	$184.80
Purchase #6	$241.64	11.413%	$269.2184	$269.22	$269.20	$269.20
Purchase #7	$176.41	6.659%	$188.1571	$188.16	$188.15	$188.20
7 purchase totals =	$1,013.97		$1,100.5176	$1,100.51	$1,100.50	$1,100.50