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	$204.47	8.312%	$221.4655	$221.47	$221.45	$221.50
Purchase #2	$92.41	3.338%	$95.4946	$95.49	$95.50	$95.50
Purchase #3	$152.46	6.457%	$162.3043	$162.30	$162.30	$162.30
Purchase #4	$202.78	12.107%	$227.3306	$227.33	$227.35	$227.30
Purchase #5	$95.41	13.545%	$108.3333	$108.33	$108.35	$108.30
Purchase #6	$32.33	12.318%	$36.3124	$36.31	$36.30	$36.30
Purchase #7	$243.98	11.742%	$272.6281	$272.63	$272.65	$272.60
7 purchase totals =	$1,023.84		$1,123.8688	$1,123.86	$1,123.90	$1,123.80