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	$29.74	7.111%	$31.8548	$31.85	$31.85	$31.90
Purchase #2	$190.25	3.392%	$196.7033	$196.70	$196.70	$196.70
Purchase #3	$175.72	7.395%	$188.7145	$188.71	$188.70	$188.70
Purchase #4	$226.75	7.506%	$243.7699	$243.77	$243.75	$243.80
Purchase #5	$94.35	10.824%	$104.5624	$104.56	$104.55	$104.60
Purchase #6	$27.97	11.144%	$31.087	$31.09	$31.10	$31.10
Purchase #7	$119.73	11.521%	$133.5241	$133.52	$133.50	$133.50
7 purchase totals =	$864.51		$930.2160	$930.20	$930.15	$930.30