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	$94.51	5.689%	$99.8867	$99.89	$99.90	$99.90
Purchase #2	$13.31	6.523%	$14.1782	$14.18	$14.20	$14.20
Purchase #3	$123.88	5.585%	$130.7987	$130.80	$130.80	$130.80
Purchase #4	$66.88	9.506%	$73.2376	$73.24	$73.25	$73.20
Purchase #5	$100.33	9.328%	$109.6888	$109.69	$109.70	$109.70
Purchase #6	$238.97	6.394%	$254.2497	$254.25	$254.25	$254.20
Purchase #7	$192.49	11.758%	$215.123	$215.12	$215.10	$215.10
7 purchase totals =	$830.37		$897.1627	$897.17	$897.20	$897.10