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	$72.25	10.288%	$79.6831	$79.68	$79.70	$79.70
Purchase #2	$165.68	10.206%	$182.5893	$182.59	$182.60	$182.60
Purchase #3	$108.64	13.515%	$123.3227	$123.32	$123.30	$123.30
Purchase #4	$174.30	11.520%	$194.3794	$194.38	$194.40	$194.40
Purchase #5	$83.56	6.621%	$89.0925	$89.09	$89.10	$89.10
Purchase #6	$245.65	6.283%	$261.0842	$261.08	$261.10	$261.10
Purchase #7	$132.99	7.657%	$143.173	$143.17	$143.15	$143.20
7 purchase totals =	$983.07		$1,073.3242	$1,073.31	$1,073.35	$1,073.40