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	$77.42	8.351%	$83.8853	$83.89	$83.90	$83.90
Purchase #2	$174.53	6.175%	$185.3072	$185.31	$185.30	$185.30
Purchase #3	$173.34	7.621%	$186.5502	$186.55	$186.55	$186.60
Purchase #4	$27.74	13.688%	$31.5371	$31.54	$31.55	$31.50
Purchase #5	$32.77	13.264%	$37.1166	$37.12	$37.10	$37.10
Purchase #6	$9.70	4.479%	$10.1345	$10.13	$10.15	$10.10
Purchase #7	$152.31	13.816%	$173.3531	$173.35	$173.35	$173.40
7 purchase totals =	$647.81		$707.8840	$707.89	$707.90	$707.90