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	$151.67	9.507%	$166.0893	$166.09	$166.10	$166.10
Purchase #2	$137.30	10.317%	$151.4652	$151.47	$151.45	$151.50
Purchase #3	$25.34	7.835%	$27.3254	$27.33	$27.35	$27.30
Purchase #4	$153.39	10.867%	$170.0589	$170.06	$170.05	$170.10
Purchase #5	$102.64	6.346%	$109.1535	$109.15	$109.15	$109.20
Purchase #6	$32.28	9.138%	$35.2297	$35.23	$35.25	$35.20
Purchase #7	$87.72	4.518%	$91.6832	$91.68	$91.70	$91.70
7 purchase totals =	$690.34		$751.0052	$751.01	$751.05	$751.10