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	$38.82	5.593%	$40.9912	$40.99	$41.00	$41.00
Purchase #2	$195.65	11.872%	$218.8776	$218.88	$218.90	$218.90
Purchase #3	$244.58	9.215%	$267.118	$267.12	$267.10	$267.10
Purchase #4	$38.91	5.113%	$40.8995	$40.90	$40.90	$40.90
Purchase #5	$45.54	12.594%	$51.2753	$51.28	$51.30	$51.30
Purchase #6	$156.56	4.848%	$164.15	$164.15	$164.15	$164.20
Purchase #7	$102.98	6.155%	$109.3184	$109.32	$109.30	$109.30
7 purchase totals =	$823.04		$892.6300	$892.64	$892.65	$892.70