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	$72.78	9.259%	$79.5187	$79.52	$79.50	$79.50
Purchase #2	$135.31	11.515%	$150.8909	$150.89	$150.90	$150.90
Purchase #3	$29.42	9.781%	$32.2976	$32.30	$32.30	$32.30
Purchase #4	$180.70	5.684%	$190.971	$190.97	$190.95	$191.00
Purchase #5	$102.29	3.136%	$105.4978	$105.50	$105.50	$105.50
Purchase #6	$218.34	8.307%	$236.4775	$236.48	$236.50	$236.50
Purchase #7	$244.44	3.544%	$253.103	$253.10	$253.10	$253.10
7 purchase totals =	$983.28		$1,048.7565	$1,048.76	$1,048.75	$1,048.80