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	$48.88	13.432%	$55.4456	$55.45	$55.45	$55.40
Purchase #2	$55.89	6.566%	$59.5597	$59.56	$59.55	$59.60
Purchase #3	$174.36	4.179%	$181.6465	$181.65	$181.65	$181.60
Purchase #4	$19.51	10.368%	$21.5328	$21.53	$21.55	$21.50
Purchase #5	$33.62	12.196%	$37.7203	$37.72	$37.70	$37.70
Purchase #6	$238.39	3.349%	$246.3737	$246.37	$246.35	$246.40
Purchase #7	$118.60	4.585%	$124.0378	$124.04	$124.05	$124.00
7 purchase totals =	$689.25		$726.3164	$726.32	$726.30	$726.20