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	$224.83	11.674%	$251.0767	$251.08	$251.10	$251.10
Purchase #2	$136.47	7.252%	$146.3668	$146.37	$146.35	$146.40
Purchase #3	$165.51	4.123%	$172.334	$172.33	$172.35	$172.30
Purchase #4	$181.66	3.666%	$188.3197	$188.32	$188.30	$188.30
Purchase #5	$198.54	5.360%	$209.1817	$209.18	$209.20	$209.20
Purchase #6	$65.77	9.593%	$72.0793	$72.08	$72.10	$72.10
Purchase #7	$139.68	12.651%	$157.3509	$157.35	$157.35	$157.40
7 purchase totals =	$1,112.46		$1,196.7091	$1,196.71	$1,196.75	$1,196.80