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	$221.54	10.746%	$245.3467	$245.35	$245.35	$245.30
Purchase #2	$49.34	4.402%	$51.5119	$51.51	$51.50	$51.50
Purchase #3	$112.64	9.322%	$123.1403	$123.14	$123.15	$123.10
Purchase #4	$221.76	13.117%	$250.8483	$250.85	$250.85	$250.80
Purchase #5	$213.44	4.622%	$223.3052	$223.31	$223.30	$223.30
Purchase #6	$73.58	10.859%	$81.5701	$81.57	$81.55	$81.60
Purchase #7	$106.98	7.814%	$115.3394	$115.34	$115.35	$115.30
7 purchase totals =	$999.28		$1,091.0619	$1,091.07	$1,091.05	$1,090.90