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	$169.36	12.698%	$190.8653	$190.87	$190.85	$190.90
Purchase #2	$42.82	11.441%	$47.719	$47.72	$47.70	$47.70
Purchase #3	$64.25	10.385%	$70.9224	$70.92	$70.90	$70.90
Purchase #4	$59.93	6.506%	$63.829	$63.83	$63.85	$63.80
Purchase #5	$166.83	10.809%	$184.8627	$184.86	$184.85	$184.90
Purchase #6	$79.80	7.236%	$85.5743	$85.57	$85.55	$85.60
Purchase #7	$123.64	13.861%	$140.7777	$140.78	$140.80	$140.80
7 purchase totals =	$706.63		$784.5504	$784.55	$784.50	$784.60