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	$235.92	10.851%	$261.5197	$261.52	$261.50	$261.50
Purchase #2	$196.33	13.393%	$222.6245	$222.62	$222.60	$222.60
Purchase #3	$139.83	4.274%	$145.8063	$145.81	$145.80	$145.80
Purchase #4	$192.80	7.118%	$206.5235	$206.52	$206.50	$206.50
Purchase #5	$96.63	9.836%	$106.1345	$106.13	$106.15	$106.10
Purchase #6	$31.93	5.699%	$33.7497	$33.75	$33.75	$33.70
Purchase #7	$41.90	11.874%	$46.8752	$46.88	$46.90	$46.90
7 purchase totals =	$935.34		$1,023.2334	$1,023.23	$1,023.20	$1,023.10