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	$162.80	7.591%	$175.1581	$175.16	$175.15	$175.20
Purchase #2	$18.85	8.612%	$20.4734	$20.47	$20.45	$20.50
Purchase #3	$188.64	6.324%	$200.5696	$200.57	$200.55	$200.60
Purchase #4	$122.97	6.648%	$131.145	$131.15	$131.15	$131.10
Purchase #5	$153.88	10.741%	$170.4083	$170.41	$170.40	$170.40
Purchase #6	$102.67	9.354%	$112.2738	$112.27	$112.25	$112.30
Purchase #7	$86.93	13.727%	$98.8629	$98.86	$98.85	$98.90
7 purchase totals =	$836.74		$908.8911	$908.89	$908.80	$909.00