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	$45.48	7.360%	$48.8273	$48.83	$48.85	$48.80
Purchase #2	$96.57	13.562%	$109.6668	$109.67	$109.65	$109.70
Purchase #3	$116.59	3.369%	$120.5179	$120.52	$120.50	$120.50
Purchase #4	$192.58	7.260%	$206.5613	$206.56	$206.55	$206.60
Purchase #5	$180.61	10.166%	$198.9708	$198.97	$198.95	$199.00
Purchase #6	$134.53	12.129%	$150.8471	$150.85	$150.85	$150.80
Purchase #7	$198.40	13.315%	$224.817	$224.82	$224.80	$224.80
7 purchase totals =	$964.76		$1,060.2082	$1,060.22	$1,060.15	$1,060.20