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	$199.41	12.557%	$224.4499	$224.45	$224.45	$224.40
Purchase #2	$214.68	11.424%	$239.205	$239.21	$239.20	$239.20
Purchase #3	$89.52	7.760%	$96.4668	$96.47	$96.45	$96.50
Purchase #4	$191.37	7.354%	$205.4433	$205.44	$205.45	$205.40
Purchase #5	$66.52	9.249%	$72.6724	$72.67	$72.65	$72.70
Purchase #6	$181.28	7.196%	$194.3249	$194.32	$194.30	$194.30
Purchase #7	$144.32	13.754%	$164.1698	$164.17	$164.15	$164.20
7 purchase totals =	$1,087.10		$1,196.7321	$1,196.73	$1,196.65	$1,196.70