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	$193.89	4.820%	$203.2355	$203.24	$203.25	$203.20
Purchase #2	$6.73	8.263%	$7.2861	$7.29	$7.30	$7.30
Purchase #3	$159.98	6.647%	$170.6139	$170.61	$170.60	$170.60
Purchase #4	$72.86	7.711%	$78.4782	$78.48	$78.50	$78.50
Purchase #5	$130.81	13.551%	$148.5361	$148.54	$148.55	$148.50
Purchase #6	$38.56	8.862%	$41.9772	$41.98	$42.00	$42.00
Purchase #7	$131.54	6.628%	$140.2585	$140.26	$140.25	$140.30
7 purchase totals =	$734.37		$790.3855	$790.40	$790.45	$790.40