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	$63.27	3.113%	$65.2396	$65.24	$65.25	$65.20
Purchase #2	$81.64	4.653%	$85.4387	$85.44	$85.45	$85.40
Purchase #3	$168.35	10.792%	$186.5183	$186.52	$186.50	$186.50
Purchase #4	$52.82	5.365%	$55.6538	$55.65	$55.65	$55.70
Purchase #5	$33.84	8.612%	$36.7543	$36.75	$36.75	$36.80
Purchase #6	$231.30	5.271%	$243.4918	$243.49	$243.50	$243.50
Purchase #7	$229.64	4.656%	$240.332	$240.33	$240.35	$240.30
7 purchase totals =	$860.86		$913.4285	$913.42	$913.45	$913.40