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	$217.55	9.448%	$238.1041	$238.10	$238.10	$238.10
Purchase #2	$156.82	9.528%	$171.7618	$171.76	$171.75	$171.80
Purchase #3	$249.82	9.408%	$273.3231	$273.32	$273.30	$273.30
Purchase #4	$97.85	7.702%	$105.3864	$105.39	$105.40	$105.40
Purchase #5	$90.69	8.227%	$98.1511	$98.15	$98.15	$98.20
Purchase #6	$57.36	11.209%	$63.7895	$63.79	$63.80	$63.80
Purchase #7	$170.40	6.286%	$181.1113	$181.11	$181.10	$181.10
7 purchase totals =	$1,040.49		$1,131.6273	$1,131.62	$1,131.60	$1,131.70