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	$235.26	13.396%	$266.7754	$266.78	$266.80	$266.80
Purchase #2	$25.89	10.681%	$28.6553	$28.66	$28.65	$28.70
Purchase #3	$178.54	5.567%	$188.4793	$188.48	$188.50	$188.50
Purchase #4	$134.47	9.608%	$147.3899	$147.39	$147.40	$147.40
Purchase #5	$128.89	8.625%	$140.0068	$140.01	$140.00	$140.00
Purchase #6	$190.43	12.339%	$213.9272	$213.93	$213.95	$213.90
Purchase #7	$80.76	10.532%	$89.2656	$89.27	$89.25	$89.30
7 purchase totals =	$974.24		$1,074.4995	$1,074.52	$1,074.55	$1,074.60