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	$180.44	10.243%	$198.9225	$198.92	$198.90	$198.90
Purchase #2	$157.76	10.558%	$174.4163	$174.42	$174.40	$174.40
Purchase #3	$40.43	3.821%	$41.9748	$41.97	$41.95	$42.00
Purchase #4	$196.27	9.804%	$215.5123	$215.51	$215.50	$215.50
Purchase #5	$109.93	4.113%	$114.4514	$114.45	$114.45	$114.50
Purchase #6	$227.64	13.435%	$258.2234	$258.22	$258.20	$258.20
Purchase #7	$195.34	12.348%	$219.4606	$219.46	$219.45	$219.50
7 purchase totals =	$1,107.81		$1,222.9613	$1,222.95	$1,222.85	$1,223.00