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	$179.97	11.404%	$200.4938	$200.49	$200.50	$200.50
Purchase #2	$185.64	3.551%	$192.2321	$192.23	$192.25	$192.20
Purchase #3	$165.43	7.704%	$178.1747	$178.17	$178.15	$178.20
Purchase #4	$65.99	10.405%	$72.8563	$72.86	$72.85	$72.90
Purchase #5	$170.39	3.143%	$175.7454	$175.75	$175.75	$175.70
Purchase #6	$196.72	13.773%	$223.8142	$223.81	$223.80	$223.80
Purchase #7	$147.72	7.275%	$158.4666	$158.47	$158.45	$158.50
7 purchase totals =	$1,111.86		$1,201.7831	$1,201.78	$1,201.75	$1,201.80