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	$81.88	4.463%	$85.5343	$85.53	$85.55	$85.50
Purchase #2	$43.98	11.757%	$49.1507	$49.15	$49.15	$49.20
Purchase #3	$250.78	7.726%	$270.1553	$270.16	$270.15	$270.20
Purchase #4	$18.39	3.643%	$19.0599	$19.06	$19.05	$19.10
Purchase #5	$120.77	6.312%	$128.393	$128.39	$128.40	$128.40
Purchase #6	$214.39	6.698%	$228.7498	$228.75	$228.75	$228.70
Purchase #7	$185.78	5.651%	$196.2784	$196.28	$196.30	$196.30
7 purchase totals =	$915.97		$977.3214	$977.32	$977.35	$977.40