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	$151.32	3.717%	$156.9446	$156.94	$156.95	$156.90
Purchase #2	$144.48	9.119%	$157.6551	$157.66	$157.65	$157.70
Purchase #3	$76.46	5.336%	$80.5399	$80.54	$80.55	$80.50
Purchase #4	$228.72	7.315%	$245.4509	$245.45	$245.45	$245.50
Purchase #5	$68.33	5.586%	$72.1469	$72.15	$72.15	$72.10
Purchase #6	$100.94	3.133%	$104.1025	$104.10	$104.10	$104.10
Purchase #7	$37.75	12.481%	$42.4616	$42.46	$42.45	$42.50
7 purchase totals =	$808.00		$859.3015	$859.30	$859.30	$859.30