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	$119.38	4.361%	$124.5862	$124.59	$124.60	$124.60
Purchase #2	$165.67	3.507%	$171.48	$171.48	$171.50	$171.50
Purchase #3	$88.63	6.647%	$94.5212	$94.52	$94.50	$94.50
Purchase #4	$229.73	6.758%	$245.2552	$245.26	$245.25	$245.30
Purchase #5	$65.90	8.630%	$71.5872	$71.59	$71.60	$71.60
Purchase #6	$134.70	6.353%	$143.2575	$143.26	$143.25	$143.30
Purchase #7	$211.28	11.191%	$234.9243	$234.92	$234.90	$234.90
7 purchase totals =	$1,015.29		$1,085.6116	$1,085.62	$1,085.60	$1,085.70