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	$56.70	12.323%	$63.6871	$63.69	$63.70	$63.70
Purchase #2	$101.90	7.282%	$109.3204	$109.32	$109.30	$109.30
Purchase #3	$135.55	11.796%	$151.5395	$151.54	$151.55	$151.50
Purchase #4	$201.95	5.425%	$212.9058	$212.91	$212.90	$212.90
Purchase #5	$7.31	7.577%	$7.8639	$7.86	$7.85	$7.90
Purchase #6	$227.83	9.348%	$249.1275	$249.13	$249.15	$249.10
Purchase #7	$234.36	8.852%	$255.1055	$255.11	$255.10	$255.10
7 purchase totals =	$965.60		$1,049.5497	$1,049.56	$1,049.55	$1,049.50