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	$118.54	10.790%	$131.3305	$131.33	$131.35	$131.30
Purchase #2	$90.98	4.414%	$94.9959	$95.00	$95.00	$95.00
Purchase #3	$137.89	10.551%	$152.4388	$152.44	$152.45	$152.40
Purchase #4	$214.79	3.772%	$222.8919	$222.89	$222.90	$222.90
Purchase #5	$226.40	3.805%	$235.0145	$235.01	$235.00	$235.00
Purchase #6	$247.79	9.806%	$272.0883	$272.09	$272.10	$272.10
Purchase #7	$106.88	12.278%	$120.0027	$120.00	$120.00	$120.00
7 purchase totals =	$1,143.27		$1,228.7626	$1,228.76	$1,228.80	$1,228.70