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	$112.96	5.560%	$119.2406	$119.24	$119.25	$119.20
Purchase #2	$12.33	6.121%	$13.0847	$13.08	$13.10	$13.10
Purchase #3	$18.71	7.451%	$20.1041	$20.10	$20.10	$20.10
Purchase #4	$31.96	4.369%	$33.3563	$33.36	$33.35	$33.40
Purchase #5	$188.40	6.197%	$200.0751	$200.08	$200.10	$200.10
Purchase #6	$153.30	12.816%	$172.9469	$172.95	$172.95	$172.90
Purchase #7	$27.48	13.199%	$31.1071	$31.11	$31.10	$31.10
7 purchase totals =	$545.14		$589.9148	$589.92	$589.95	$589.90