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	$109.33	4.218%	$113.9415	$113.94	$113.95	$113.90
Purchase #2	$97.43	8.419%	$105.6326	$105.63	$105.65	$105.60
Purchase #3	$42.25	4.351%	$44.0883	$44.09	$44.10	$44.10
Purchase #4	$9.60	8.872%	$10.4517	$10.45	$10.45	$10.50
Purchase #5	$59.31	11.755%	$66.2819	$66.28	$66.30	$66.30
Purchase #6	$71.43	3.362%	$73.8315	$73.83	$73.85	$73.80
Purchase #7	$182.60	8.692%	$198.4716	$198.47	$198.45	$198.50
7 purchase totals =	$571.95		$612.6991	$612.69	$612.75	$612.70