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	$211.37	3.602%	$218.9835	$218.98	$219.00	$219.00
Purchase #2	$16.61	8.549%	$18.03	$18.03	$18.05	$18.00
Purchase #3	$162.61	10.399%	$179.5198	$179.52	$179.50	$179.50
Purchase #4	$102.85	8.374%	$111.4627	$111.46	$111.45	$111.50
Purchase #5	$207.99	6.872%	$222.2831	$222.28	$222.30	$222.30
Purchase #6	$55.32	11.455%	$61.6569	$61.66	$61.65	$61.70
Purchase #7	$45.48	11.437%	$50.6815	$50.68	$50.70	$50.70
7 purchase totals =	$802.23		$862.6175	$862.61	$862.65	$862.70