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	$245.96	5.483%	$259.446	$259.45	$259.45	$259.40
Purchase #2	$39.62	10.699%	$43.8589	$43.86	$43.85	$43.90
Purchase #3	$19.39	6.519%	$20.654	$20.65	$20.65	$20.70
Purchase #4	$89.50	11.662%	$99.9375	$99.94	$99.95	$99.90
Purchase #5	$12.81	12.733%	$14.4411	$14.44	$14.45	$14.40
Purchase #6	$44.98	5.702%	$47.5448	$47.54	$47.55	$47.50
Purchase #7	$212.92	7.870%	$229.6768	$229.68	$229.70	$229.70
7 purchase totals =	$665.18		$715.5591	$715.56	$715.60	$715.50