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	$69.64	12.713%	$78.4933	$78.49	$78.50	$78.50
Purchase #2	$83.73	10.265%	$92.3249	$92.32	$92.30	$92.30
Purchase #3	$205.30	8.467%	$222.6828	$222.68	$222.70	$222.70
Purchase #4	$195.25	12.201%	$219.0725	$219.07	$219.05	$219.10
Purchase #5	$215.91	3.162%	$222.7371	$222.74	$222.75	$222.70
Purchase #6	$248.60	13.260%	$281.5644	$281.56	$281.55	$281.60
Purchase #7	$99.33	10.293%	$109.554	$109.55	$109.55	$109.60
7 purchase totals =	$1,117.76		$1,226.4290	$1,226.41	$1,226.40	$1,226.50