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	$241.73	7.563%	$260.012	$260.01	$260.00	$260.00
Purchase #2	$100.62	8.842%	$109.5168	$109.52	$109.50	$109.50
Purchase #3	$193.48	6.118%	$205.3171	$205.32	$205.30	$205.30
Purchase #4	$101.82	5.715%	$107.639	$107.64	$107.65	$107.60
Purchase #5	$233.39	12.497%	$262.5567	$262.56	$262.55	$262.60
Purchase #6	$209.78	4.132%	$218.4481	$218.45	$218.45	$218.40
Purchase #7	$131.56	4.364%	$137.3013	$137.30	$137.30	$137.30
7 purchase totals =	$1,212.38		$1,300.7910	$1,300.80	$1,300.75	$1,300.70