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	$217.27	7.412%	$233.3741	$233.37	$233.35	$233.40
Purchase #2	$155.52	7.830%	$167.6972	$167.70	$167.70	$167.70
Purchase #3	$172.62	5.658%	$182.3868	$182.39	$182.40	$182.40
Purchase #4	$169.46	10.591%	$187.4075	$187.41	$187.40	$187.40
Purchase #5	$29.97	4.852%	$31.4241	$31.42	$31.40	$31.40
Purchase #6	$101.25	13.333%	$114.7497	$114.75	$114.75	$114.70
Purchase #7	$111.89	7.133%	$119.8711	$119.87	$119.85	$119.90
7 purchase totals =	$957.98		$1,036.9105	$1,036.91	$1,036.85	$1,036.90