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	$70.85	9.445%	$77.5418	$77.54	$77.55	$77.50
Purchase #2	$18.34	6.282%	$19.4921	$19.49	$19.50	$19.50
Purchase #3	$183.32	5.138%	$192.739	$192.74	$192.75	$192.70
Purchase #4	$44.27	11.387%	$49.311	$49.31	$49.30	$49.30
Purchase #5	$77.69	5.737%	$82.1471	$82.15	$82.15	$82.10
Purchase #6	$89.87	9.199%	$98.1371	$98.14	$98.15	$98.10
Purchase #7	$12.38	5.365%	$13.0442	$13.04	$13.05	$13.00
7 purchase totals =	$496.72		$532.4123	$532.41	$532.45	$532.20