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	$71.86	9.488%	$78.6781	$78.68	$78.70	$78.70
Purchase #2	$222.63	10.622%	$246.2778	$246.28	$246.30	$246.30
Purchase #3	$39.68	6.380%	$42.2116	$42.21	$42.20	$42.20
Purchase #4	$244.91	5.260%	$257.7923	$257.79	$257.80	$257.80
Purchase #5	$68.45	10.371%	$75.5489	$75.55	$75.55	$75.50
Purchase #6	$61.31	9.717%	$67.2675	$67.27	$67.25	$67.30
Purchase #7	$150.59	9.719%	$165.2258	$165.23	$165.25	$165.20
7 purchase totals =	$859.43		$933.0020	$933.01	$933.05	$933.00