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	$10.73	6.749%	$11.4542	$11.45	$11.45	$11.50
Purchase #2	$112.27	13.818%	$127.7835	$127.78	$127.80	$127.80
Purchase #3	$25.82	5.649%	$27.2786	$27.28	$27.30	$27.30
Purchase #4	$85.35	8.694%	$92.7703	$92.77	$92.75	$92.80
Purchase #5	$103.90	5.796%	$109.922	$109.92	$109.90	$109.90
Purchase #6	$58.78	12.378%	$66.0558	$66.06	$66.05	$66.10
Purchase #7	$38.49	7.696%	$41.4522	$41.45	$41.45	$41.50
7 purchase totals =	$435.34		$476.7166	$476.71	$476.70	$476.90