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	$180.46	5.352%	$190.1182	$190.12	$190.10	$190.10
Purchase #2	$146.97	11.609%	$164.0317	$164.03	$164.05	$164.00
Purchase #3	$167.79	12.164%	$188.2	$188.20	$188.20	$188.20
Purchase #4	$18.65	10.206%	$20.5534	$20.55	$20.55	$20.60
Purchase #5	$199.89	9.717%	$219.3133	$219.31	$219.30	$219.30
Purchase #6	$238.79	6.874%	$255.2044	$255.20	$255.20	$255.20
Purchase #7	$79.84	7.456%	$85.7929	$85.79	$85.80	$85.80
7 purchase totals =	$1,032.39		$1,123.2139	$1,123.20	$1,123.20	$1,123.20