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	$59.64	7.648%	$64.2013	$64.20	$64.20	$64.20
Purchase #2	$38.51	11.345%	$42.879	$42.88	$42.90	$42.90
Purchase #3	$67.77	7.420%	$72.7985	$72.80	$72.80	$72.80
Purchase #4	$152.96	7.553%	$164.5131	$164.51	$164.50	$164.50
Purchase #5	$80.47	3.625%	$83.387	$83.39	$83.40	$83.40
Purchase #6	$183.37	8.671%	$199.27	$199.27	$199.25	$199.30
Purchase #7	$154.25	7.444%	$165.7324	$165.73	$165.75	$165.70
7 purchase totals =	$736.97		$792.7813	$792.78	$792.80	$792.80