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	$138.28	7.152%	$148.1698	$148.17	$148.15	$148.20
Purchase #2	$66.51	9.172%	$72.6103	$72.61	$72.60	$72.60
Purchase #3	$240.84	8.346%	$260.9405	$260.94	$260.95	$260.90
Purchase #4	$34.88	7.417%	$37.467	$37.47	$37.45	$37.50
Purchase #5	$31.56	11.263%	$35.1146	$35.11	$35.10	$35.10
Purchase #6	$232.44	4.281%	$242.3908	$242.39	$242.40	$242.40
Purchase #7	$205.51	7.192%	$220.2903	$220.29	$220.30	$220.30
7 purchase totals =	$950.02		$1,016.9833	$1,016.98	$1,016.95	$1,017.00