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	$101.64	7.553%	$109.3169	$109.32	$109.30	$109.30
Purchase #2	$218.63	5.353%	$230.3333	$230.33	$230.35	$230.30
Purchase #3	$18.92	13.681%	$21.5084	$21.51	$21.50	$21.50
Purchase #4	$232.98	7.783%	$251.1128	$251.11	$251.10	$251.10
Purchase #5	$97.43	12.832%	$109.9322	$109.93	$109.95	$109.90
Purchase #6	$243.71	9.192%	$266.1118	$266.11	$266.10	$266.10
Purchase #7	$52.25	13.112%	$59.101	$59.10	$59.10	$59.10
7 purchase totals =	$965.56		$1,047.4164	$1,047.41	$1,047.40	$1,047.30