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	$153.86	13.511%	$174.648	$174.65	$174.65	$174.60
Purchase #2	$87.67	12.654%	$98.7638	$98.76	$98.75	$98.80
Purchase #3	$214.37	4.439%	$223.8859	$223.89	$223.90	$223.90
Purchase #4	$29.64	10.873%	$32.8628	$32.86	$32.85	$32.90
Purchase #5	$160.53	4.299%	$167.4312	$167.43	$167.45	$167.40
Purchase #6	$80.40	8.618%	$87.3289	$87.33	$87.35	$87.30
Purchase #7	$185.55	13.866%	$211.2784	$211.28	$211.30	$211.30
7 purchase totals =	$912.02		$996.1990	$996.20	$996.25	$996.20