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	$111.33	4.706%	$116.5692	$116.57	$116.55	$116.60
Purchase #2	$160.76	9.721%	$176.3875	$176.39	$176.40	$176.40
Purchase #3	$95.59	3.614%	$99.0446	$99.04	$99.05	$99.00
Purchase #4	$10.96	12.870%	$12.3706	$12.37	$12.35	$12.40
Purchase #5	$90.58	12.346%	$101.763	$101.76	$101.75	$101.80
Purchase #6	$128.32	3.837%	$133.2436	$133.24	$133.25	$133.20
Purchase #7	$217.48	12.259%	$244.1409	$244.14	$244.15	$244.10
7 purchase totals =	$815.02		$883.5194	$883.51	$883.50	$883.50