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	$181.95	5.553%	$192.0537	$192.05	$192.05	$192.10
Purchase #2	$175.41	8.623%	$190.5356	$190.54	$190.55	$190.50
Purchase #3	$106.45	4.676%	$111.4276	$111.43	$111.45	$111.40
Purchase #4	$5.40	9.174%	$5.8954	$5.90	$5.90	$5.90
Purchase #5	$220.79	12.308%	$247.9648	$247.96	$247.95	$248.00
Purchase #6	$91.82	5.194%	$96.5891	$96.59	$96.60	$96.60
Purchase #7	$47.98	12.741%	$54.0931	$54.09	$54.10	$54.10
7 purchase totals =	$829.80		$898.5593	$898.56	$898.60	$898.60