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	$147.50	12.243%	$165.5584	$165.56	$165.55	$165.60
Purchase #2	$194.49	12.591%	$218.9782	$218.98	$219.00	$219.00
Purchase #3	$200.97	13.686%	$228.4748	$228.47	$228.45	$228.50
Purchase #4	$83.45	13.257%	$94.513	$94.51	$94.50	$94.50
Purchase #5	$109.89	4.671%	$115.023	$115.02	$115.00	$115.00
Purchase #6	$54.76	11.512%	$61.064	$61.06	$61.05	$61.10
Purchase #7	$167.79	5.679%	$177.3188	$177.32	$177.30	$177.30
7 purchase totals =	$958.85		$1,060.9302	$1,060.92	$1,060.85	$1,061.00