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	$152.61	5.816%	$161.4858	$161.49	$161.50	$161.50
Purchase #2	$57.72	12.383%	$64.8675	$64.87	$64.85	$64.90
Purchase #3	$246.25	13.459%	$279.3928	$279.39	$279.40	$279.40
Purchase #4	$198.90	8.378%	$215.5638	$215.56	$215.55	$215.60
Purchase #5	$83.38	10.136%	$91.8314	$91.83	$91.85	$91.80
Purchase #6	$26.46	9.335%	$28.93	$28.93	$28.95	$28.90
Purchase #7	$181.34	13.333%	$205.5181	$205.52	$205.50	$205.50
7 purchase totals =	$946.66		$1,047.5894	$1,047.59	$1,047.60	$1,047.60