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	$162.57	3.218%	$167.8015	$167.80	$167.80	$167.80
Purchase #2	$32.61	10.112%	$35.9075	$35.91	$35.90	$35.90
Purchase #3	$171.92	11.764%	$192.1447	$192.14	$192.15	$192.10
Purchase #4	$184.55	5.455%	$194.6172	$194.62	$194.60	$194.60
Purchase #5	$225.70	13.784%	$256.8105	$256.81	$256.80	$256.80
Purchase #6	$88.74	4.731%	$92.9383	$92.94	$92.95	$92.90
Purchase #7	$73.88	5.676%	$78.0734	$78.07	$78.05	$78.10
7 purchase totals =	$939.97		$1,018.2931	$1,018.29	$1,018.25	$1,018.20