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	$157.65	5.157%	$165.78	$165.78	$165.80	$165.80
Purchase #2	$84.91	6.535%	$90.4589	$90.46	$90.45	$90.50
Purchase #3	$139.81	12.702%	$157.5687	$157.57	$157.55	$157.60
Purchase #4	$177.86	4.224%	$185.3728	$185.37	$185.35	$185.40
Purchase #5	$79.31	7.140%	$84.9727	$84.97	$84.95	$85.00
Purchase #6	$174.80	11.741%	$195.3233	$195.32	$195.30	$195.30
Purchase #7	$250.38	4.857%	$262.541	$262.54	$262.55	$262.50
7 purchase totals =	$1,064.72		$1,142.0174	$1,142.01	$1,141.95	$1,142.10