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	$97.85	3.257%	$101.037	$101.04	$101.05	$101.00
Purchase #2	$200.92	7.386%	$215.76	$215.76	$215.75	$215.80
Purchase #3	$206.52	8.315%	$223.6921	$223.69	$223.70	$223.70
Purchase #4	$39.33	5.189%	$41.3708	$41.37	$41.35	$41.40
Purchase #5	$76.87	12.482%	$86.4649	$86.46	$86.45	$86.50
Purchase #6	$54.25	9.207%	$59.2448	$59.24	$59.25	$59.20
Purchase #7	$113.52	6.401%	$120.7864	$120.79	$120.80	$120.80
7 purchase totals =	$789.26		$848.3560	$848.35	$848.35	$848.40