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	$103.72	7.111%	$111.0955	$111.10	$111.10	$111.10
Purchase #2	$234.58	3.314%	$242.354	$242.35	$242.35	$242.40
Purchase #3	$125.56	4.795%	$131.5806	$131.58	$131.60	$131.60
Purchase #4	$160.95	8.425%	$174.51	$174.51	$174.50	$174.50
Purchase #5	$127.77	6.144%	$135.6202	$135.62	$135.60	$135.60
Purchase #6	$239.73	6.423%	$255.1279	$255.13	$255.15	$255.10
Purchase #7	$200.38	3.181%	$206.7541	$206.75	$206.75	$206.80
7 purchase totals =	$1,192.69		$1,257.0423	$1,257.04	$1,257.05	$1,257.10