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	$173.39	10.576%	$191.7277	$191.73	$191.75	$191.70
Purchase #2	$67.98	4.390%	$70.9643	$70.96	$70.95	$71.00
Purchase #3	$205.39	6.261%	$218.2495	$218.25	$218.25	$218.20
Purchase #4	$246.74	13.688%	$280.5138	$280.51	$280.50	$280.50
Purchase #5	$148.39	8.288%	$160.6886	$160.69	$160.70	$160.70
Purchase #6	$23.59	8.380%	$25.5668	$25.57	$25.55	$25.60
Purchase #7	$112.52	5.107%	$118.2664	$118.27	$118.25	$118.30
7 purchase totals =	$978.00		$1,065.9771	$1,065.98	$1,065.95	$1,066.00