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	$181.47	13.259%	$205.5311	$205.53	$205.55	$205.50
Purchase #2	$57.61	6.273%	$61.2239	$61.22	$61.20	$61.20
Purchase #3	$180.37	13.456%	$204.6406	$204.64	$204.65	$204.60
Purchase #4	$101.38	13.256%	$114.8189	$114.82	$114.80	$114.80
Purchase #5	$196.63	6.456%	$209.3244	$209.32	$209.30	$209.30
Purchase #6	$136.45	6.663%	$145.5417	$145.54	$145.55	$145.50
Purchase #7	$236.44	3.386%	$244.4459	$244.45	$244.45	$244.40
7 purchase totals =	$1,090.35		$1,185.5265	$1,185.52	$1,185.50	$1,185.30