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	$69.79	4.316%	$72.8021	$72.80	$72.80	$72.80
Purchase #2	$86.34	10.289%	$95.2235	$95.22	$95.20	$95.20
Purchase #3	$241.32	13.363%	$273.5676	$273.57	$273.55	$273.60
Purchase #4	$53.70	6.453%	$57.1653	$57.17	$57.15	$57.20
Purchase #5	$142.86	5.595%	$150.853	$150.85	$150.85	$150.90
Purchase #6	$215.57	7.460%	$231.6515	$231.65	$231.65	$231.70
Purchase #7	$223.30	12.692%	$251.6412	$251.64	$251.65	$251.60
7 purchase totals =	$1,032.88		$1,132.9042	$1,132.90	$1,132.85	$1,133.00