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	$41.68	4.250%	$43.4514	$43.45	$43.45	$43.50
Purchase #2	$175.72	7.123%	$188.2365	$188.24	$188.25	$188.20
Purchase #3	$178.44	7.206%	$191.2984	$191.30	$191.30	$191.30
Purchase #4	$125.27	4.353%	$130.723	$130.72	$130.70	$130.70
Purchase #5	$52.37	6.391%	$55.717	$55.72	$55.70	$55.70
Purchase #6	$25.38	6.592%	$27.053	$27.05	$27.05	$27.10
Purchase #7	$227.78	13.455%	$258.4278	$258.43	$258.45	$258.40
7 purchase totals =	$826.64		$894.9071	$894.91	$894.90	$894.90