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	$217.28	5.630%	$229.5129	$229.51	$229.50	$229.50
Purchase #2	$200.34	3.417%	$207.1856	$207.19	$207.20	$207.20
Purchase #3	$131.34	7.630%	$141.3612	$141.36	$141.35	$141.40
Purchase #4	$244.77	6.331%	$260.2664	$260.27	$260.25	$260.30
Purchase #5	$114.28	11.367%	$127.2702	$127.27	$127.25	$127.30
Purchase #6	$151.32	11.389%	$168.5538	$168.55	$168.55	$168.60
Purchase #7	$90.73	10.373%	$100.1414	$100.14	$100.15	$100.10
7 purchase totals =	$1,150.06		$1,234.2915	$1,234.29	$1,234.25	$1,234.40