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	$70.62	8.628%	$76.7131	$76.71	$76.70	$76.70
Purchase #2	$87.98	11.436%	$98.0414	$98.04	$98.05	$98.00
Purchase #3	$43.54	4.392%	$45.4523	$45.45	$45.45	$45.50
Purchase #4	$53.94	5.229%	$56.7605	$56.76	$56.75	$56.80
Purchase #5	$83.32	3.742%	$86.4378	$86.44	$86.45	$86.40
Purchase #6	$196.59	3.842%	$204.143	$204.14	$204.15	$204.10
Purchase #7	$38.87	10.530%	$42.963	$42.96	$42.95	$43.00
7 purchase totals =	$574.86		$610.5111	$610.50	$610.50	$610.50