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	$173.61	9.593%	$190.2644	$190.26	$190.25	$190.30
Purchase #2	$68.46	5.271%	$72.0685	$72.07	$72.05	$72.10
Purchase #3	$95.53	7.165%	$102.3747	$102.37	$102.35	$102.40
Purchase #4	$130.95	9.791%	$143.7713	$143.77	$143.75	$143.80
Purchase #5	$174.32	7.732%	$187.7984	$187.80	$187.80	$187.80
Purchase #6	$181.52	5.154%	$190.8755	$190.88	$190.90	$190.90
Purchase #7	$167.73	3.481%	$173.5687	$173.57	$173.55	$173.60
7 purchase totals =	$992.12		$1,060.7215	$1,060.72	$1,060.65	$1,060.90