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	$211.28	3.186%	$218.0114	$218.01	$218.00	$218.00
Purchase #2	$98.36	5.150%	$103.4255	$103.43	$103.45	$103.40
Purchase #3	$102.76	3.788%	$106.6525	$106.65	$106.65	$106.70
Purchase #4	$65.71	10.181%	$72.3999	$72.40	$72.40	$72.40
Purchase #5	$35.54	11.629%	$39.6729	$39.67	$39.65	$39.70
Purchase #6	$239.66	4.352%	$250.09	$250.09	$250.10	$250.10
Purchase #7	$248.58	6.181%	$263.9447	$263.94	$263.95	$263.90
7 purchase totals =	$1,001.89		$1,054.1969	$1,054.19	$1,054.20	$1,054.20