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	$152.52	7.186%	$163.4801	$163.48	$163.50	$163.50
Purchase #2	$189.70	10.826%	$210.2369	$210.24	$210.25	$210.20
Purchase #3	$228.36	4.484%	$238.5997	$238.60	$238.60	$238.60
Purchase #4	$91.82	5.510%	$96.8793	$96.88	$96.90	$96.90
Purchase #5	$216.34	12.573%	$243.5404	$243.54	$243.55	$243.50
Purchase #6	$45.66	12.451%	$51.3451	$51.35	$51.35	$51.30
Purchase #7	$64.26	5.651%	$67.8913	$67.89	$67.90	$67.90
7 purchase totals =	$988.66		$1,071.9728	$1,071.98	$1,072.05	$1,071.90