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	$63.59	10.200%	$70.0762	$70.08	$70.10	$70.10
Purchase #2	$17.47	6.128%	$18.5406	$18.54	$18.55	$18.50
Purchase #3	$188.28	12.183%	$211.2182	$211.22	$211.20	$211.20
Purchase #4	$206.74	6.378%	$219.9259	$219.93	$219.95	$219.90
Purchase #5	$80.89	9.399%	$88.4929	$88.49	$88.50	$88.50
Purchase #6	$46.27	13.414%	$52.4767	$52.48	$52.50	$52.50
Purchase #7	$88.45	13.351%	$100.259	$100.26	$100.25	$100.30
7 purchase totals =	$691.69		$760.9895	$761.00	$761.05	$761.00