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	$234.82	12.623%	$264.4613	$264.46	$264.45	$264.50
Purchase #2	$212.37	3.175%	$219.1127	$219.11	$219.10	$219.10
Purchase #3	$64.62	12.767%	$72.87	$72.87	$72.85	$72.90
Purchase #4	$95.35	3.754%	$98.9294	$98.93	$98.95	$98.90
Purchase #5	$206.38	3.121%	$212.8211	$212.82	$212.80	$212.80
Purchase #6	$45.78	4.574%	$47.874	$47.87	$47.85	$47.90
Purchase #7	$87.66	7.490%	$94.2257	$94.23	$94.25	$94.20
7 purchase totals =	$946.98		$1,010.2942	$1,010.29	$1,010.25	$1,010.30