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	$191.78	4.294%	$200.015	$200.02	$200.00	$200.00
Purchase #2	$23.51	6.676%	$25.0795	$25.08	$25.10	$25.10
Purchase #3	$35.54	8.153%	$38.4376	$38.44	$38.45	$38.40
Purchase #4	$210.56	5.821%	$222.8167	$222.82	$222.80	$222.80
Purchase #5	$178.49	12.303%	$200.4496	$200.45	$200.45	$200.40
Purchase #6	$222.61	3.425%	$230.2344	$230.23	$230.25	$230.20
Purchase #7	$51.67	7.111%	$55.3443	$55.34	$55.35	$55.30
7 purchase totals =	$914.16		$972.3771	$972.38	$972.40	$972.20