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	$248.30	5.164%	$261.1222	$261.12	$261.10	$261.10
Purchase #2	$63.98	12.662%	$72.0811	$72.08	$72.10	$72.10
Purchase #3	$109.67	3.693%	$113.7201	$113.72	$113.70	$113.70
Purchase #4	$182.74	3.303%	$188.7759	$188.78	$188.80	$188.80
Purchase #5	$113.49	8.731%	$123.3988	$123.40	$123.40	$123.40
Purchase #6	$39.28	4.723%	$41.1352	$41.14	$41.15	$41.10
Purchase #7	$220.47	13.234%	$249.647	$249.65	$249.65	$249.60
7 purchase totals =	$977.93		$1,049.8803	$1,049.89	$1,049.90	$1,049.80