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	$42.97	13.469%	$48.7576	$48.76	$48.75	$48.80
Purchase #2	$220.59	10.378%	$243.4828	$243.48	$243.50	$243.50
Purchase #3	$41.56	3.867%	$43.1671	$43.17	$43.15	$43.20
Purchase #4	$139.78	12.592%	$157.3811	$157.38	$157.40	$157.40
Purchase #5	$143.29	9.279%	$156.5859	$156.59	$156.60	$156.60
Purchase #6	$62.36	5.631%	$65.8715	$65.87	$65.85	$65.90
Purchase #7	$18.96	6.723%	$20.2347	$20.23	$20.25	$20.20
7 purchase totals =	$669.51		$735.4807	$735.48	$735.50	$735.60