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	$232.50	13.599%	$264.1177	$264.12	$264.10	$264.10
Purchase #2	$100.47	10.591%	$111.1108	$111.11	$111.10	$111.10
Purchase #3	$93.63	10.466%	$103.4293	$103.43	$103.45	$103.40
Purchase #4	$181.90	12.373%	$204.4065	$204.41	$204.40	$204.40
Purchase #5	$19.44	10.614%	$21.5034	$21.50	$21.50	$21.50
Purchase #6	$202.84	12.712%	$228.625	$228.63	$228.65	$228.60
Purchase #7	$94.72	5.615%	$100.0385	$100.04	$100.05	$100.00
7 purchase totals =	$925.50		$1,033.2312	$1,033.24	$1,033.25	$1,033.10