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	$56.88	9.874%	$62.4963	$62.50	$62.50	$62.50
Purchase #2	$211.72	7.576%	$227.7599	$227.76	$227.75	$227.80
Purchase #3	$144.87	4.266%	$151.0502	$151.05	$151.05	$151.10
Purchase #4	$213.54	11.613%	$238.3384	$238.34	$238.35	$238.30
Purchase #5	$56.25	4.809%	$58.9551	$58.96	$58.95	$59.00
Purchase #6	$159.37	6.551%	$169.8103	$169.81	$169.80	$169.80
Purchase #7	$102.34	7.225%	$109.7341	$109.73	$109.75	$109.70
7 purchase totals =	$944.97		$1,018.1443	$1,018.15	$1,018.15	$1,018.20