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	$89.90	4.578%	$94.0156	$94.02	$94.00	$94.00
Purchase #2	$85.40	6.408%	$90.8724	$90.87	$90.85	$90.90
Purchase #3	$243.82	7.665%	$262.5088	$262.51	$262.50	$262.50
Purchase #4	$226.63	10.620%	$250.6981	$250.70	$250.70	$250.70
Purchase #5	$249.98	11.795%	$279.4651	$279.47	$279.45	$279.50
Purchase #6	$134.90	7.608%	$145.1632	$145.16	$145.15	$145.20
Purchase #7	$46.26	6.215%	$49.1351	$49.14	$49.15	$49.10
7 purchase totals =	$1,076.89		$1,171.8583	$1,171.87	$1,171.80	$1,171.90