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	$61.40	12.710%	$69.2039	$69.20	$69.20	$69.20
Purchase #2	$125.53	4.767%	$131.514	$131.51	$131.50	$131.50
Purchase #3	$137.87	9.601%	$151.1069	$151.11	$151.10	$151.10
Purchase #4	$77.33	6.288%	$82.1925	$82.19	$82.20	$82.20
Purchase #5	$129.89	9.842%	$142.6738	$142.67	$142.65	$142.70
Purchase #6	$68.40	5.588%	$72.2222	$72.22	$72.20	$72.20
Purchase #7	$6.81	11.851%	$7.6171	$7.62	$7.60	$7.60
7 purchase totals =	$607.23		$656.5304	$656.52	$656.45	$656.50