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	$66.87	7.800%	$72.0859	$72.09	$72.10	$72.10
Purchase #2	$212.87	6.695%	$227.1216	$227.12	$227.10	$227.10
Purchase #3	$245.56	12.511%	$276.282	$276.28	$276.30	$276.30
Purchase #4	$28.96	10.760%	$32.0761	$32.08	$32.10	$32.10
Purchase #5	$156.88	7.628%	$168.8468	$168.85	$168.85	$168.80
Purchase #6	$139.98	9.810%	$153.712	$153.71	$153.70	$153.70
Purchase #7	$129.52	3.371%	$133.8861	$133.89	$133.90	$133.90
7 purchase totals =	$980.64		$1,064.0105	$1,064.02	$1,064.05	$1,064.00