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	$86.59	11.781%	$96.7912	$96.79	$96.80	$96.80
Purchase #2	$231.38	4.514%	$241.8245	$241.82	$241.80	$241.80
Purchase #3	$60.85	10.383%	$67.1681	$67.17	$67.15	$67.20
Purchase #4	$187.61	11.726%	$209.6091	$209.61	$209.60	$209.60
Purchase #5	$149.76	8.525%	$162.527	$162.53	$162.55	$162.50
Purchase #6	$109.53	6.560%	$116.7152	$116.72	$116.70	$116.70
Purchase #7	$244.38	6.149%	$259.4069	$259.41	$259.40	$259.40
7 purchase totals =	$1,070.10		$1,154.0420	$1,154.05	$1,154.00	$1,154.00