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	$199.41	4.591%	$208.5649	$208.56	$208.55	$208.60
Purchase #2	$76.59	5.202%	$80.5742	$80.57	$80.55	$80.60
Purchase #3	$89.72	11.857%	$100.3581	$100.36	$100.35	$100.40
Purchase #4	$6.42	7.841%	$6.9234	$6.92	$6.90	$6.90
Purchase #5	$6.25	10.309%	$6.8943	$6.89	$6.90	$6.90
Purchase #6	$54.77	12.547%	$61.642	$61.64	$61.65	$61.60
Purchase #7	$103.79	7.264%	$111.3293	$111.33	$111.35	$111.30
7 purchase totals =	$536.95		$576.2862	$576.27	$576.25	$576.30