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	$224.36	11.682%	$250.5697	$250.57	$250.55	$250.60
Purchase #2	$42.66	6.339%	$45.3642	$45.36	$45.35	$45.40
Purchase #3	$113.51	6.472%	$120.8564	$120.86	$120.85	$120.90
Purchase #4	$51.35	5.200%	$54.0202	$54.02	$54.00	$54.00
Purchase #5	$246.99	5.154%	$259.7199	$259.72	$259.70	$259.70
Purchase #6	$245.90	12.466%	$276.5539	$276.55	$276.55	$276.60
Purchase #7	$57.48	4.314%	$59.9597	$59.96	$59.95	$60.00
7 purchase totals =	$982.25		$1,067.0440	$1,067.04	$1,066.95	$1,067.20