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	$57.57	7.836%	$62.0812	$62.08	$62.10	$62.10
Purchase #2	$134.45	13.780%	$152.9772	$152.98	$153.00	$153.00
Purchase #3	$199.78	6.861%	$213.4869	$213.49	$213.50	$213.50
Purchase #4	$93.71	6.596%	$99.8911	$99.89	$99.90	$99.90
Purchase #5	$45.27	13.394%	$51.3335	$51.33	$51.35	$51.30
Purchase #6	$246.64	11.338%	$274.604	$274.60	$274.60	$274.60
Purchase #7	$30.72	9.732%	$33.7097	$33.71	$33.70	$33.70
7 purchase totals =	$808.14		$888.0836	$888.08	$888.15	$888.10