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	$191.35	7.507%	$205.7146	$205.71	$205.70	$205.70
Purchase #2	$141.59	13.402%	$160.5659	$160.57	$160.55	$160.60
Purchase #3	$181.79	5.517%	$191.8194	$191.82	$191.80	$191.80
Purchase #4	$57.34	4.411%	$59.8693	$59.87	$59.85	$59.90
Purchase #5	$108.64	3.294%	$112.2186	$112.22	$112.20	$112.20
Purchase #6	$230.39	7.671%	$248.0632	$248.06	$248.05	$248.10
Purchase #7	$62.30	7.358%	$66.884	$66.88	$66.90	$66.90
7 purchase totals =	$973.40		$1,045.1350	$1,045.13	$1,045.05	$1,045.20