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	$144.30	11.253%	$160.5381	$160.54	$160.55	$160.50
Purchase #2	$223.60	9.387%	$244.5893	$244.59	$244.60	$244.60
Purchase #3	$69.74	13.418%	$79.0977	$79.10	$79.10	$79.10
Purchase #4	$65.50	11.180%	$72.8229	$72.82	$72.80	$72.80
Purchase #5	$90.47	10.351%	$99.8345	$99.83	$99.85	$99.80
Purchase #6	$54.29	5.561%	$57.3091	$57.31	$57.30	$57.30
Purchase #7	$217.54	7.862%	$234.643	$234.64	$234.65	$234.60
7 purchase totals =	$865.44		$948.8346	$948.83	$948.85	$948.70