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	$129.75	11.624%	$144.8321	$144.83	$144.85	$144.80
Purchase #2	$141.52	7.530%	$152.1765	$152.18	$152.20	$152.20
Purchase #3	$135.32	6.336%	$143.8939	$143.89	$143.90	$143.90
Purchase #4	$244.63	13.460%	$277.5572	$277.56	$277.55	$277.60
Purchase #5	$60.61	6.112%	$64.3145	$64.31	$64.30	$64.30
Purchase #6	$226.27	5.117%	$237.8482	$237.85	$237.85	$237.80
Purchase #7	$41.90	11.565%	$46.7457	$46.75	$46.75	$46.70
7 purchase totals =	$980.00		$1,067.3681	$1,067.37	$1,067.40	$1,067.30