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	$199.33	8.227%	$215.7289	$215.73	$215.75	$215.70
Purchase #2	$127.63	11.436%	$142.2258	$142.23	$142.25	$142.20
Purchase #3	$249.38	8.435%	$270.4152	$270.42	$270.40	$270.40
Purchase #4	$99.90	4.798%	$104.6932	$104.69	$104.70	$104.70
Purchase #5	$81.38	9.475%	$89.0908	$89.09	$89.10	$89.10
Purchase #6	$129.69	3.672%	$134.4522	$134.45	$134.45	$134.50
Purchase #7	$94.94	9.416%	$103.8796	$103.88	$103.90	$103.90
7 purchase totals =	$982.25		$1,060.4857	$1,060.49	$1,060.55	$1,060.50