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	$248.57	13.627%	$282.4426	$282.44	$282.45	$282.40
Purchase #2	$65.38	7.805%	$70.4829	$70.48	$70.50	$70.50
Purchase #3	$220.54	13.683%	$250.7165	$250.72	$250.70	$250.70
Purchase #4	$83.93	12.601%	$94.506	$94.51	$94.50	$94.50
Purchase #5	$165.29	5.707%	$174.7231	$174.72	$174.70	$174.70
Purchase #6	$88.34	9.779%	$96.9788	$96.98	$97.00	$97.00
Purchase #7	$103.31	11.757%	$115.4562	$115.46	$115.45	$115.50
7 purchase totals =	$975.36		$1,085.3061	$1,085.31	$1,085.30	$1,085.30