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	$243.35	4.307%	$253.8311	$253.83	$253.85	$253.80
Purchase #2	$85.52	4.250%	$89.1546	$89.15	$89.15	$89.20
Purchase #3	$25.47	12.825%	$28.7365	$28.74	$28.75	$28.70
Purchase #4	$38.99	13.422%	$44.2232	$44.22	$44.20	$44.20
Purchase #5	$175.32	11.162%	$194.8892	$194.89	$194.90	$194.90
Purchase #6	$153.72	11.300%	$171.0904	$171.09	$171.10	$171.10
Purchase #7	$205.65	4.751%	$215.4204	$215.42	$215.40	$215.40
7 purchase totals =	$928.02		$997.3454	$997.34	$997.35	$997.30