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	$144.34	4.805%	$151.2755	$151.28	$151.30	$151.30
Purchase #2	$132.87	6.188%	$141.092	$141.09	$141.10	$141.10
Purchase #3	$9.96	5.713%	$10.529	$10.53	$10.55	$10.50
Purchase #4	$53.32	10.749%	$59.0514	$59.05	$59.05	$59.10
Purchase #5	$207.85	7.761%	$223.9812	$223.98	$224.00	$224.00
Purchase #6	$112.74	6.780%	$120.3838	$120.38	$120.40	$120.40
Purchase #7	$55.31	10.665%	$61.2088	$61.21	$61.20	$61.20
7 purchase totals =	$716.39		$767.5217	$767.52	$767.60	$767.60