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	$227.97	10.380%	$251.6333	$251.63	$251.65	$251.60
Purchase #2	$72.50	13.804%	$82.5079	$82.51	$82.50	$82.50
Purchase #3	$84.85	8.220%	$91.8247	$91.82	$91.80	$91.80
Purchase #4	$53.65	11.209%	$59.6636	$59.66	$59.65	$59.70
Purchase #5	$156.96	5.682%	$165.8785	$165.88	$165.90	$165.90
Purchase #6	$47.59	7.466%	$51.1431	$51.14	$51.15	$51.10
Purchase #7	$35.89	4.185%	$37.392	$37.39	$37.40	$37.40
7 purchase totals =	$679.41		$740.0431	$740.03	$740.05	$740.00