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	$181.47	10.345%	$200.2431	$200.24	$200.25	$200.20
Purchase #2	$64.51	8.649%	$70.0895	$70.09	$70.10	$70.10
Purchase #3	$73.70	13.815%	$83.8817	$83.88	$83.90	$83.90
Purchase #4	$247.88	4.641%	$259.3841	$259.38	$259.40	$259.40
Purchase #5	$238.28	7.507%	$256.1677	$256.17	$256.15	$256.20
Purchase #6	$46.29	4.794%	$48.5091	$48.51	$48.50	$48.50
Purchase #7	$92.79	10.163%	$102.2202	$102.22	$102.20	$102.20
7 purchase totals =	$944.92		$1,020.4954	$1,020.49	$1,020.50	$1,020.50