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	$124.90	13.730%	$142.0488	$142.05	$142.05	$142.00
Purchase #2	$114.83	3.152%	$118.4494	$118.45	$118.45	$118.40
Purchase #3	$114.73	8.738%	$124.7551	$124.76	$124.75	$124.80
Purchase #4	$150.67	10.362%	$166.2824	$166.28	$166.30	$166.30
Purchase #5	$54.62	12.798%	$61.6103	$61.61	$61.60	$61.60
Purchase #6	$186.77	13.628%	$212.223	$212.22	$212.20	$212.20
Purchase #7	$28.62	12.369%	$32.16	$32.16	$32.15	$32.20
7 purchase totals =	$775.14		$857.5290	$857.53	$857.50	$857.50