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	$36.93	3.112%	$38.0793	$38.08	$38.10	$38.10
Purchase #2	$121.32	8.148%	$131.2052	$131.21	$131.20	$131.20
Purchase #3	$174.50	12.438%	$196.2043	$196.20	$196.20	$196.20
Purchase #4	$94.43	6.367%	$100.4424	$100.44	$100.45	$100.40
Purchase #5	$35.43	6.108%	$37.5941	$37.59	$37.60	$37.60
Purchase #6	$187.37	13.424%	$212.5225	$212.52	$212.50	$212.50
Purchase #7	$86.80	8.425%	$94.1129	$94.11	$94.10	$94.10
7 purchase totals =	$736.78		$810.1607	$810.15	$810.15	$810.10