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	$186.43	7.441%	$200.3023	$200.30	$200.30	$200.30
Purchase #2	$191.61	6.526%	$204.1145	$204.11	$204.10	$204.10
Purchase #3	$141.80	10.257%	$156.3444	$156.34	$156.35	$156.30
Purchase #4	$120.51	9.410%	$131.85	$131.85	$131.85	$131.90
Purchase #5	$139.25	10.157%	$153.3936	$153.39	$153.40	$153.40
Purchase #6	$216.83	10.114%	$238.7602	$238.76	$238.75	$238.80
Purchase #7	$99.42	6.239%	$105.6228	$105.62	$105.60	$105.60
7 purchase totals =	$1,095.85		$1,190.3878	$1,190.37	$1,190.35	$1,190.40