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	$134.59	8.345%	$145.8215	$145.82	$145.80	$145.80
Purchase #2	$49.51	9.253%	$54.0912	$54.09	$54.10	$54.10
Purchase #3	$186.91	6.406%	$198.8835	$198.88	$198.90	$198.90
Purchase #4	$87.72	12.872%	$99.0113	$99.01	$99.00	$99.00
Purchase #5	$247.64	3.445%	$256.1712	$256.17	$256.15	$256.20
Purchase #6	$239.39	11.781%	$267.5925	$267.59	$267.60	$267.60
Purchase #7	$213.81	13.435%	$242.5354	$242.54	$242.55	$242.50
7 purchase totals =	$1,159.57		$1,264.1066	$1,264.10	$1,264.10	$1,264.10