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	$185.63	8.692%	$201.765	$201.77	$201.75	$201.80
Purchase #2	$116.55	8.194%	$126.1001	$126.10	$126.10	$126.10
Purchase #3	$99.89	5.555%	$105.4389	$105.44	$105.45	$105.40
Purchase #4	$51.94	5.564%	$54.8299	$54.83	$54.85	$54.80
Purchase #5	$83.62	10.548%	$92.4402	$92.44	$92.45	$92.40
Purchase #6	$72.98	7.346%	$78.3411	$78.34	$78.35	$78.30
Purchase #7	$160.85	11.352%	$179.1097	$179.11	$179.10	$179.10
7 purchase totals =	$771.46		$838.0249	$838.03	$838.05	$837.90