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	$85.73	6.820%	$91.5768	$91.58	$91.60	$91.60
Purchase #2	$115.48	13.662%	$131.2569	$131.26	$131.25	$131.30
Purchase #3	$249.42	11.434%	$277.9387	$277.94	$277.95	$277.90
Purchase #4	$124.72	13.443%	$141.4861	$141.49	$141.50	$141.50
Purchase #5	$185.64	11.607%	$207.1872	$207.19	$207.20	$207.20
Purchase #6	$137.88	10.153%	$151.879	$151.88	$151.90	$151.90
Purchase #7	$213.60	11.717%	$238.6275	$238.63	$238.65	$238.60
7 purchase totals =	$1,112.47		$1,239.9522	$1,239.97	$1,240.05	$1,240.00