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	$159.80	5.648%	$168.8255	$168.83	$168.85	$168.80
Purchase #2	$83.76	9.653%	$91.8454	$91.85	$91.85	$91.80
Purchase #3	$151.86	8.488%	$164.7499	$164.75	$164.75	$164.70
Purchase #4	$9.75	6.808%	$10.4138	$10.41	$10.40	$10.40
Purchase #5	$250.38	12.601%	$281.9304	$281.93	$281.95	$281.90
Purchase #6	$222.59	8.437%	$241.3699	$241.37	$241.35	$241.40
Purchase #7	$81.67	6.300%	$86.8152	$86.82	$86.80	$86.80
7 purchase totals =	$959.81		$1,045.9501	$1,045.96	$1,045.95	$1,045.80