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	$223.54	6.738%	$238.6021	$238.60	$238.60	$238.60
Purchase #2	$153.40	4.439%	$160.2094	$160.21	$160.20	$160.20
Purchase #3	$66.60	8.815%	$72.4708	$72.47	$72.45	$72.50
Purchase #4	$146.40	12.152%	$164.1905	$164.19	$164.20	$164.20
Purchase #5	$99.88	6.437%	$106.3093	$106.31	$106.30	$106.30
Purchase #6	$115.97	6.368%	$123.355	$123.36	$123.35	$123.40
Purchase #7	$209.40	13.737%	$238.1653	$238.17	$238.15	$238.20
7 purchase totals =	$1,015.19		$1,103.3024	$1,103.31	$1,103.25	$1,103.40