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	$119.29	10.753%	$132.1173	$132.12	$132.10	$132.10
Purchase #2	$100.84	11.557%	$112.4941	$112.49	$112.50	$112.50
Purchase #3	$71.74	9.774%	$78.7519	$78.75	$78.75	$78.80
Purchase #4	$87.68	12.348%	$98.5067	$98.51	$98.50	$98.50
Purchase #5	$116.97	10.428%	$129.1676	$129.17	$129.15	$129.20
Purchase #6	$190.62	13.220%	$215.82	$215.82	$215.80	$215.80
Purchase #7	$246.27	10.663%	$272.5298	$272.53	$272.55	$272.50
7 purchase totals =	$933.41		$1,039.3874	$1,039.39	$1,039.35	$1,039.40