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	$186.44	9.353%	$203.8777	$203.88	$203.90	$203.90
Purchase #2	$98.62	3.259%	$101.834	$101.83	$101.85	$101.80
Purchase #3	$46.44	9.595%	$50.8959	$50.90	$50.90	$50.90
Purchase #4	$19.84	10.411%	$21.9055	$21.91	$21.90	$21.90
Purchase #5	$233.91	4.141%	$243.5962	$243.60	$243.60	$243.60
Purchase #6	$175.27	5.682%	$185.2288	$185.23	$185.25	$185.20
Purchase #7	$206.27	4.794%	$216.1586	$216.16	$216.15	$216.20
7 purchase totals =	$966.79		$1,023.4967	$1,023.51	$1,023.55	$1,023.50