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	$164.57	13.143%	$186.1994	$186.20	$186.20	$186.20
Purchase #2	$54.43	10.135%	$59.9465	$59.95	$59.95	$59.90
Purchase #3	$156.66	8.297%	$169.6581	$169.66	$169.65	$169.70
Purchase #4	$154.48	9.760%	$169.5572	$169.56	$169.55	$169.60
Purchase #5	$150.75	11.334%	$167.836	$167.84	$167.85	$167.80
Purchase #6	$190.26	10.186%	$209.6399	$209.64	$209.65	$209.60
Purchase #7	$196.30	9.777%	$215.4923	$215.49	$215.50	$215.50
7 purchase totals =	$1,067.45		$1,178.3294	$1,178.34	$1,178.35	$1,178.30