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	$142.35	13.844%	$162.0569	$162.06	$162.05	$162.10
Purchase #2	$85.53	8.725%	$92.9925	$92.99	$93.00	$93.00
Purchase #3	$189.84	13.275%	$215.0413	$215.04	$215.05	$215.00
Purchase #4	$28.51	13.824%	$32.4512	$32.45	$32.45	$32.50
Purchase #5	$41.62	12.401%	$46.7813	$46.78	$46.80	$46.80
Purchase #6	$167.91	7.351%	$180.2531	$180.25	$180.25	$180.30
Purchase #7	$57.43	4.247%	$59.8691	$59.87	$59.85	$59.90
7 purchase totals =	$713.19		$789.4454	$789.44	$789.45	$789.60