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	$209.82	12.680%	$236.4252	$236.43	$236.45	$236.40
Purchase #2	$82.59	3.511%	$85.4897	$85.49	$85.50	$85.50
Purchase #3	$196.39	6.745%	$209.6365	$209.64	$209.65	$209.60
Purchase #4	$19.89	13.416%	$22.5584	$22.56	$22.55	$22.60
Purchase #5	$105.97	5.726%	$112.0378	$112.04	$112.05	$112.00
Purchase #6	$189.29	11.703%	$211.4426	$211.44	$211.45	$211.40
Purchase #7	$96.32	5.393%	$101.5145	$101.51	$101.50	$101.50
7 purchase totals =	$900.27		$979.1047	$979.11	$979.15	$979.00