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	$146.77	3.816%	$152.3707	$152.37	$152.35	$152.40
Purchase #2	$98.71	6.637%	$105.2614	$105.26	$105.25	$105.30
Purchase #3	$219.43	10.764%	$243.0494	$243.05	$243.05	$243.00
Purchase #4	$167.37	8.757%	$182.0266	$182.03	$182.05	$182.00
Purchase #5	$171.59	6.604%	$182.9218	$182.92	$182.90	$182.90
Purchase #6	$134.43	5.591%	$141.946	$141.95	$141.95	$141.90
Purchase #7	$74.36	12.741%	$83.8342	$83.83	$83.85	$83.80
7 purchase totals =	$1,012.66		$1,091.4101	$1,091.41	$1,091.40	$1,091.30