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	$52.93	8.639%	$57.5026	$57.50	$57.50	$57.50
Purchase #2	$236.98	11.150%	$263.4033	$263.40	$263.40	$263.40
Purchase #3	$39.98	5.501%	$42.1793	$42.18	$42.20	$42.20
Purchase #4	$213.46	13.337%	$241.9292	$241.93	$241.95	$241.90
Purchase #5	$137.50	9.864%	$151.063	$151.06	$151.05	$151.10
Purchase #6	$69.54	13.157%	$78.6894	$78.69	$78.70	$78.70
Purchase #7	$215.75	4.735%	$225.9658	$225.97	$225.95	$226.00
7 purchase totals =	$966.14		$1,060.7326	$1,060.73	$1,060.75	$1,060.80