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	$196.52	8.531%	$213.2851	$213.29	$213.30	$213.30
Purchase #2	$137.79	12.154%	$154.537	$154.54	$154.55	$154.50
Purchase #3	$85.73	3.189%	$88.4639	$88.46	$88.45	$88.50
Purchase #4	$92.85	11.488%	$103.5166	$103.52	$103.50	$103.50
Purchase #5	$226.87	3.118%	$233.9438	$233.94	$233.95	$233.90
Purchase #6	$200.77	8.213%	$217.2592	$217.26	$217.25	$217.30
Purchase #7	$168.78	6.198%	$179.241	$179.24	$179.25	$179.20
7 purchase totals =	$1,109.31		$1,190.2466	$1,190.25	$1,190.25	$1,190.20