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	$156.28	6.651%	$166.6742	$166.67	$166.65	$166.70
Purchase #2	$138.92	8.816%	$151.1672	$151.17	$151.15	$151.20
Purchase #3	$64.37	13.278%	$72.917	$72.92	$72.90	$72.90
Purchase #4	$56.94	3.837%	$59.1248	$59.12	$59.10	$59.10
Purchase #5	$22.33	6.636%	$23.8118	$23.81	$23.80	$23.80
Purchase #6	$68.41	3.204%	$70.6019	$70.60	$70.60	$70.60
Purchase #7	$167.48	6.741%	$178.7698	$178.77	$178.75	$178.80
7 purchase totals =	$674.73		$723.0667	$723.06	$722.95	$723.10