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	$31.82	11.283%	$35.4103	$35.41	$35.40	$35.40
Purchase #2	$43.61	3.310%	$45.0535	$45.05	$45.05	$45.10
Purchase #3	$53.30	3.322%	$55.0706	$55.07	$55.05	$55.10
Purchase #4	$74.82	9.834%	$82.1778	$82.18	$82.20	$82.20
Purchase #5	$211.54	6.264%	$224.7909	$224.79	$224.80	$224.80
Purchase #6	$138.53	3.516%	$143.4007	$143.40	$143.40	$143.40
Purchase #7	$5.99	6.546%	$6.3821	$6.38	$6.40	$6.40
7 purchase totals =	$559.61		$592.2859	$592.28	$592.30	$592.40