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	$205.98	11.165%	$228.9777	$228.98	$229.00	$229.00
Purchase #2	$20.43	13.600%	$23.2085	$23.21	$23.20	$23.20
Purchase #3	$67.57	7.713%	$72.7817	$72.78	$72.80	$72.80
Purchase #4	$141.92	3.247%	$146.5281	$146.53	$146.55	$146.50
Purchase #5	$140.65	11.204%	$156.4084	$156.41	$156.40	$156.40
Purchase #6	$33.87	11.127%	$37.6387	$37.64	$37.65	$37.60
Purchase #7	$236.38	11.318%	$263.1335	$263.13	$263.15	$263.10
7 purchase totals =	$846.80		$928.6766	$928.68	$928.75	$928.60