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	$85.28	4.651%	$89.2464	$89.25	$89.25	$89.20
Purchase #2	$93.92	4.589%	$98.23	$98.23	$98.25	$98.20
Purchase #3	$25.38	13.115%	$28.7086	$28.71	$28.70	$28.70
Purchase #4	$25.82	11.437%	$28.773	$28.77	$28.75	$28.80
Purchase #5	$59.38	6.724%	$63.3727	$63.37	$63.35	$63.40
Purchase #6	$109.33	7.416%	$117.4379	$117.44	$117.45	$117.40
Purchase #7	$16.77	5.545%	$17.6999	$17.70	$17.70	$17.70
7 purchase totals =	$415.88		$443.4685	$443.47	$443.45	$443.40