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	$245.38	4.120%	$255.4897	$255.49	$255.50	$255.50
Purchase #2	$48.52	7.789%	$52.2992	$52.30	$52.30	$52.30
Purchase #3	$90.90	11.471%	$101.3271	$101.33	$101.35	$101.30
Purchase #4	$36.42	11.571%	$40.6342	$40.63	$40.65	$40.60
Purchase #5	$79.48	8.118%	$85.9322	$85.93	$85.95	$85.90
Purchase #6	$218.26	4.382%	$227.8242	$227.82	$227.80	$227.80
Purchase #7	$248.88	6.172%	$264.2409	$264.24	$264.25	$264.20
7 purchase totals =	$967.84		$1,027.7475	$1,027.74	$1,027.80	$1,027.60