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	$226.47	7.664%	$243.8267	$243.83	$243.85	$243.80
Purchase #2	$88.29	7.179%	$94.6283	$94.63	$94.65	$94.60
Purchase #3	$124.96	6.331%	$132.8712	$132.87	$132.85	$132.90
Purchase #4	$33.61	4.709%	$35.1927	$35.19	$35.20	$35.20
Purchase #5	$63.66	12.739%	$71.7696	$71.77	$71.75	$71.80
Purchase #6	$35.64	8.289%	$38.5942	$38.59	$38.60	$38.60
Purchase #7	$81.89	8.588%	$88.9227	$88.92	$88.90	$88.90
7 purchase totals =	$654.52		$705.8054	$705.80	$705.80	$705.80