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	$5.50	8.138%	$5.9476	$5.95	$5.95	$5.90
Purchase #2	$186.83	11.550%	$208.4089	$208.41	$208.40	$208.40
Purchase #3	$30.45	4.161%	$31.717	$31.72	$31.70	$31.70
Purchase #4	$85.58	5.627%	$90.3956	$90.40	$90.40	$90.40
Purchase #5	$165.88	13.454%	$188.1975	$188.20	$188.20	$188.20
Purchase #6	$41.33	10.161%	$45.5295	$45.53	$45.55	$45.50
Purchase #7	$176.31	11.122%	$195.9192	$195.92	$195.90	$195.90
7 purchase totals =	$691.88		$766.1153	$766.13	$766.10	$766.00