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	$250.88	9.173%	$273.8932	$273.89	$273.90	$273.90
Purchase #2	$209.98	6.267%	$223.1394	$223.14	$223.15	$223.10
Purchase #3	$151.65	13.347%	$171.8907	$171.89	$171.90	$171.90
Purchase #4	$98.68	13.684%	$112.1834	$112.18	$112.20	$112.20
Purchase #5	$134.78	11.440%	$150.1988	$150.20	$150.20	$150.20
Purchase #6	$154.89	6.761%	$165.3621	$165.36	$165.35	$165.40
Purchase #7	$50.87	9.374%	$55.6386	$55.64	$55.65	$55.60
7 purchase totals =	$1,051.73		$1,152.3062	$1,152.30	$1,152.35	$1,152.30