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	$84.62	7.824%	$91.2407	$91.24	$91.25	$91.20
Purchase #2	$88.70	13.352%	$100.5432	$100.54	$100.55	$100.50
Purchase #3	$87.55	12.613%	$98.5927	$98.59	$98.60	$98.60
Purchase #4	$62.93	4.301%	$65.6366	$65.64	$65.65	$65.60
Purchase #5	$131.54	4.588%	$137.5751	$137.58	$137.60	$137.60
Purchase #6	$222.55	6.608%	$237.2561	$237.26	$237.25	$237.30
Purchase #7	$189.77	3.683%	$196.7592	$196.76	$196.75	$196.80
7 purchase totals =	$867.66		$927.6036	$927.61	$927.65	$927.60