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	$105.39	8.782%	$114.6453	$114.65	$114.65	$114.60
Purchase #2	$244.70	6.132%	$259.705	$259.71	$259.70	$259.70
Purchase #3	$24.86	6.416%	$26.455	$26.46	$26.45	$26.50
Purchase #4	$63.40	6.159%	$67.3048	$67.30	$67.30	$67.30
Purchase #5	$116.56	12.268%	$130.8596	$130.86	$130.85	$130.90
Purchase #6	$232.87	6.448%	$247.8855	$247.89	$247.90	$247.90
Purchase #7	$55.67	7.573%	$59.8859	$59.89	$59.90	$59.90
7 purchase totals =	$843.45		$906.7411	$906.76	$906.75	$906.80