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	$96.76	3.829%	$100.4649	$100.46	$100.45	$100.50
Purchase #2	$60.44	12.173%	$67.7974	$67.80	$67.80	$67.80
Purchase #3	$188.35	9.723%	$206.6633	$206.66	$206.65	$206.70
Purchase #4	$50.37	3.769%	$52.2684	$52.27	$52.25	$52.30
Purchase #5	$213.33	3.658%	$221.1336	$221.13	$221.15	$221.10
Purchase #6	$163.87	13.573%	$186.1121	$186.11	$186.10	$186.10
Purchase #7	$90.33	9.671%	$99.0658	$99.07	$99.05	$99.10
7 purchase totals =	$863.45		$933.5055	$933.50	$933.45	$933.60