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	$154.73	6.712%	$165.1155	$165.12	$165.10	$165.10
Purchase #2	$82.60	5.238%	$86.9266	$86.93	$86.95	$86.90
Purchase #3	$41.71	12.462%	$46.9079	$46.91	$46.90	$46.90
Purchase #4	$181.36	13.504%	$205.8509	$205.85	$205.85	$205.90
Purchase #5	$235.88	12.417%	$265.1692	$265.17	$265.15	$265.20
Purchase #6	$203.83	5.713%	$215.4748	$215.47	$215.45	$215.50
Purchase #7	$27.88	13.172%	$31.5524	$31.55	$31.55	$31.60
7 purchase totals =	$927.99		$1,016.9973	$1,017.00	$1,016.95	$1,017.10