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	$229.35	5.342%	$241.6019	$241.60	$241.60	$241.60
Purchase #2	$110.31	5.469%	$116.3429	$116.34	$116.35	$116.30
Purchase #3	$88.90	3.178%	$91.7252	$91.73	$91.75	$91.70
Purchase #4	$25.28	12.247%	$28.376	$28.38	$28.40	$28.40
Purchase #5	$132.55	13.527%	$150.48	$150.48	$150.50	$150.50
Purchase #6	$130.55	11.521%	$145.5907	$145.59	$145.60	$145.60
Purchase #7	$139.46	10.654%	$154.3181	$154.32	$154.30	$154.30
7 purchase totals =	$856.40		$928.4348	$928.44	$928.50	$928.40