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	$126.79	12.544%	$142.6945	$142.69	$142.70	$142.70
Purchase #2	$195.74	13.867%	$222.8833	$222.88	$222.90	$222.90
Purchase #3	$146.42	6.730%	$156.2741	$156.27	$156.25	$156.30
Purchase #4	$239.83	7.761%	$258.4432	$258.44	$258.45	$258.40
Purchase #5	$18.79	7.777%	$20.2513	$20.25	$20.25	$20.30
Purchase #6	$151.36	10.447%	$167.1726	$167.17	$167.15	$167.20
Purchase #7	$176.89	12.454%	$198.9199	$198.92	$198.90	$198.90
7 purchase totals =	$1,055.82		$1,166.6389	$1,166.62	$1,166.60	$1,166.70