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	$75.44	3.547%	$78.1159	$78.12	$78.10	$78.10
Purchase #2	$25.51	7.781%	$27.4949	$27.49	$27.50	$27.50
Purchase #3	$13.90	10.652%	$15.3806	$15.38	$15.40	$15.40
Purchase #4	$230.35	6.378%	$245.0417	$245.04	$245.05	$245.00
Purchase #5	$183.99	6.783%	$196.47	$196.47	$196.45	$196.50
Purchase #6	$198.48	12.438%	$223.1669	$223.17	$223.15	$223.20
Purchase #7	$174.72	7.528%	$187.8729	$187.87	$187.85	$187.90
7 purchase totals =	$902.39		$973.5429	$973.54	$973.50	$973.60