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	$137.26	12.123%	$153.9	$153.90	$153.90	$153.90
Purchase #2	$168.54	11.699%	$188.2575	$188.26	$188.25	$188.30
Purchase #3	$199.40	3.203%	$205.7868	$205.79	$205.80	$205.80
Purchase #4	$174.59	3.824%	$181.2663	$181.27	$181.25	$181.30
Purchase #5	$113.61	4.670%	$118.9156	$118.92	$118.90	$118.90
Purchase #6	$243.83	4.796%	$255.5241	$255.52	$255.50	$255.50
Purchase #7	$168.59	4.116%	$175.5292	$175.53	$175.55	$175.50
7 purchase totals =	$1,205.82		$1,279.1795	$1,279.19	$1,279.15	$1,279.20