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	$49.93	7.344%	$53.5969	$53.60	$53.60	$53.60
Purchase #2	$112.27	10.297%	$123.8304	$123.83	$123.85	$123.80
Purchase #3	$197.30	8.774%	$214.6111	$214.61	$214.60	$214.60
Purchase #4	$209.71	9.588%	$229.817	$229.82	$229.80	$229.80
Purchase #5	$49.66	3.677%	$51.486	$51.49	$51.50	$51.50
Purchase #6	$188.65	12.314%	$211.8804	$211.88	$211.90	$211.90
Purchase #7	$61.31	9.775%	$67.3031	$67.30	$67.30	$67.30
7 purchase totals =	$868.83		$952.5249	$952.53	$952.55	$952.50