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	$216.94	12.455%	$243.9599	$243.96	$243.95	$244.00
Purchase #2	$178.48	6.606%	$190.2704	$190.27	$190.25	$190.30
Purchase #3	$66.54	3.152%	$68.6373	$68.64	$68.65	$68.60
Purchase #4	$248.33	3.191%	$256.2542	$256.25	$256.25	$256.30
Purchase #5	$62.29	3.558%	$64.5063	$64.51	$64.50	$64.50
Purchase #6	$134.90	6.275%	$143.365	$143.37	$143.35	$143.40
Purchase #7	$52.97	11.544%	$59.0849	$59.08	$59.10	$59.10
7 purchase totals =	$960.45		$1,026.0780	$1,026.08	$1,026.05	$1,026.20