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	$68.27	4.558%	$71.3817	$71.38	$71.40	$71.40
Purchase #2	$131.31	10.333%	$144.8783	$144.88	$144.90	$144.90
Purchase #3	$105.66	5.715%	$111.6985	$111.70	$111.70	$111.70
Purchase #4	$212.63	11.787%	$237.6927	$237.69	$237.70	$237.70
Purchase #5	$147.49	13.606%	$167.5575	$167.56	$167.55	$167.60
Purchase #6	$199.96	9.320%	$218.5963	$218.60	$218.60	$218.60
Purchase #7	$89.37	11.203%	$99.3821	$99.38	$99.40	$99.40
7 purchase totals =	$954.69		$1,051.1871	$1,051.19	$1,051.25	$1,051.30