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	$228.72	13.363%	$259.2839	$259.28	$259.30	$259.30
Purchase #2	$50.89	7.217%	$54.5627	$54.56	$54.55	$54.60
Purchase #3	$223.89	8.683%	$243.3304	$243.33	$243.35	$243.30
Purchase #4	$97.59	8.342%	$105.731	$105.73	$105.75	$105.70
Purchase #5	$167.36	12.651%	$188.5327	$188.53	$188.55	$188.50
Purchase #6	$146.47	12.559%	$164.8652	$164.87	$164.85	$164.90
Purchase #7	$91.49	9.769%	$100.4277	$100.43	$100.45	$100.40
7 purchase totals =	$1,006.41		$1,116.7336	$1,116.73	$1,116.80	$1,116.70