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	$127.38	11.317%	$141.7956	$141.80	$141.80	$141.80
Purchase #2	$128.68	8.104%	$139.1082	$139.11	$139.10	$139.10
Purchase #3	$125.99	11.628%	$140.6401	$140.64	$140.65	$140.60
Purchase #4	$39.89	7.280%	$42.794	$42.79	$42.80	$42.80
Purchase #5	$249.39	12.526%	$280.6286	$280.63	$280.65	$280.60
Purchase #6	$136.76	6.415%	$145.5332	$145.53	$145.55	$145.50
Purchase #7	$151.48	10.369%	$167.187	$167.19	$167.20	$167.20
7 purchase totals =	$959.57		$1,057.6867	$1,057.69	$1,057.75	$1,057.60