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	$116.31	9.343%	$127.1768	$127.18	$127.20	$127.20
Purchase #2	$42.93	3.789%	$44.5566	$44.56	$44.55	$44.60
Purchase #3	$131.88	10.328%	$145.5006	$145.50	$145.50	$145.50
Purchase #4	$75.43	3.639%	$78.1749	$78.17	$78.15	$78.20
Purchase #5	$43.26	7.873%	$46.6659	$46.67	$46.65	$46.70
Purchase #6	$74.25	9.134%	$81.032	$81.03	$81.05	$81.00
Purchase #7	$123.68	3.321%	$127.7874	$127.79	$127.80	$127.80
7 purchase totals =	$607.74		$650.8942	$650.90	$650.90	$651.00