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	$69.64	10.126%	$76.6917	$76.69	$76.70	$76.70
Purchase #2	$32.40	9.391%	$35.4427	$35.44	$35.45	$35.40
Purchase #3	$151.72	6.864%	$162.1341	$162.13	$162.15	$162.10
Purchase #4	$46.96	13.403%	$53.254	$53.25	$53.25	$53.30
Purchase #5	$150.98	9.603%	$165.4786	$165.48	$165.50	$165.50
Purchase #6	$197.92	5.290%	$208.39	$208.39	$208.40	$208.40
Purchase #7	$97.93	3.275%	$101.1372	$101.14	$101.15	$101.10
7 purchase totals =	$747.55		$802.5283	$802.52	$802.60	$802.50