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	$127.91	12.409%	$143.7824	$143.78	$143.80	$143.80
Purchase #2	$116.49	9.532%	$127.5938	$127.59	$127.60	$127.60
Purchase #3	$237.92	3.350%	$245.8903	$245.89	$245.90	$245.90
Purchase #4	$225.75	6.663%	$240.7917	$240.79	$240.80	$240.80
Purchase #5	$113.85	11.752%	$127.2297	$127.23	$127.25	$127.20
Purchase #6	$94.71	5.791%	$100.1947	$100.19	$100.20	$100.20
Purchase #7	$94.74	12.832%	$106.897	$106.90	$106.90	$106.90
7 purchase totals =	$1,011.37		$1,092.3796	$1,092.37	$1,092.45	$1,092.40