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	$174.65	9.145%	$190.6217	$190.62	$190.60	$190.60
Purchase #2	$37.83	12.391%	$42.5175	$42.52	$42.50	$42.50
Purchase #3	$55.48	12.278%	$62.2918	$62.29	$62.30	$62.30
Purchase #4	$72.41	5.370%	$76.2984	$76.30	$76.30	$76.30
Purchase #5	$43.62	11.216%	$48.5124	$48.51	$48.50	$48.50
Purchase #6	$56.32	3.585%	$58.3391	$58.34	$58.35	$58.30
Purchase #7	$117.59	4.220%	$122.5523	$122.55	$122.55	$122.60
7 purchase totals =	$557.90		$601.1332	$601.13	$601.10	$601.10