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	$213.97	10.835%	$237.1536	$237.15	$237.15	$237.20
Purchase #2	$245.56	11.308%	$273.3279	$273.33	$273.35	$273.30
Purchase #3	$79.62	13.620%	$90.4642	$90.46	$90.45	$90.50
Purchase #4	$84.70	12.311%	$95.1274	$95.13	$95.15	$95.10
Purchase #5	$59.81	5.725%	$63.2341	$63.23	$63.25	$63.20
Purchase #6	$78.53	9.842%	$86.2589	$86.26	$86.25	$86.30
Purchase #7	$93.39	11.874%	$104.4791	$104.48	$104.50	$104.50
7 purchase totals =	$855.58		$950.0452	$950.04	$950.10	$950.10