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	$199.95	6.380%	$212.7068	$212.71	$212.70	$212.70
Purchase #2	$56.34	6.233%	$59.8517	$59.85	$59.85	$59.90
Purchase #3	$56.70	12.671%	$63.8845	$63.88	$63.90	$63.90
Purchase #4	$136.52	7.184%	$146.3276	$146.33	$146.35	$146.30
Purchase #5	$70.89	3.147%	$73.1209	$73.12	$73.10	$73.10
Purchase #6	$69.74	11.364%	$77.6653	$77.67	$77.65	$77.70
Purchase #7	$165.69	3.366%	$171.2671	$171.27	$171.25	$171.30
7 purchase totals =	$755.83		$804.8239	$804.83	$804.80	$804.90