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	$123.59	6.726%	$131.9027	$131.90	$131.90	$131.90
Purchase #2	$199.52	11.793%	$223.0494	$223.05	$223.05	$223.00
Purchase #3	$159.41	10.284%	$175.8037	$175.80	$175.80	$175.80
Purchase #4	$88.43	12.397%	$99.3927	$99.39	$99.40	$99.40
Purchase #5	$125.82	4.163%	$131.0579	$131.06	$131.05	$131.10
Purchase #6	$14.66	6.501%	$15.613	$15.61	$15.60	$15.60
Purchase #7	$208.45	12.170%	$233.8184	$233.82	$233.80	$233.80
7 purchase totals =	$919.88		$1,010.6378	$1,010.63	$1,010.60	$1,010.60