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	$187.50	9.397%	$205.1194	$205.12	$205.10	$205.10
Purchase #2	$161.87	4.123%	$168.5439	$168.54	$168.55	$168.50
Purchase #3	$179.31	6.832%	$191.5605	$191.56	$191.55	$191.60
Purchase #4	$38.68	10.712%	$42.8234	$42.82	$42.80	$42.80
Purchase #5	$158.96	10.790%	$176.1118	$176.11	$176.10	$176.10
Purchase #6	$58.43	12.609%	$65.7974	$65.80	$65.80	$65.80
Purchase #7	$230.77	7.820%	$248.8162	$248.82	$248.80	$248.80
7 purchase totals =	$1,015.52		$1,098.7726	$1,098.77	$1,098.70	$1,098.70