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	$181.90	3.547%	$188.352	$188.35	$188.35	$188.40
Purchase #2	$68.28	5.851%	$72.2751	$72.28	$72.30	$72.30
Purchase #3	$97.34	7.161%	$104.3105	$104.31	$104.30	$104.30
Purchase #4	$55.88	5.657%	$59.0411	$59.04	$59.05	$59.00
Purchase #5	$139.93	7.542%	$150.4835	$150.48	$150.50	$150.50
Purchase #6	$51.89	8.160%	$56.1242	$56.12	$56.10	$56.10
Purchase #7	$244.64	6.423%	$260.3532	$260.35	$260.35	$260.40
7 purchase totals =	$839.86		$890.9396	$890.93	$890.95	$891.00