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	$245.56	5.288%	$258.5452	$258.55	$258.55	$258.50
Purchase #2	$64.62	13.455%	$73.3146	$73.31	$73.30	$73.30
Purchase #3	$123.27	3.732%	$127.8704	$127.87	$127.85	$127.90
Purchase #4	$94.47	5.385%	$99.5572	$99.56	$99.55	$99.60
Purchase #5	$14.56	12.620%	$16.3975	$16.40	$16.40	$16.40
Purchase #6	$204.64	8.423%	$221.8768	$221.88	$221.90	$221.90
Purchase #7	$235.90	6.128%	$250.356	$250.36	$250.35	$250.40
7 purchase totals =	$983.02		$1,047.9177	$1,047.93	$1,047.90	$1,048.00