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	$102.98	8.149%	$111.3718	$111.37	$111.35	$111.40
Purchase #2	$8.73	10.278%	$9.6273	$9.63	$9.65	$9.60
Purchase #3	$48.29	5.246%	$50.8233	$50.82	$50.80	$50.80
Purchase #4	$80.80	11.252%	$89.8916	$89.89	$89.90	$89.90
Purchase #5	$86.53	11.175%	$96.1997	$96.20	$96.20	$96.20
Purchase #6	$96.56	10.681%	$106.8736	$106.87	$106.85	$106.90
Purchase #7	$212.47	4.603%	$222.25	$222.25	$222.25	$222.30
7 purchase totals =	$636.36		$687.0373	$687.03	$687.00	$687.10