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	$193.27	3.858%	$200.7264	$200.73	$200.75	$200.70
Purchase #2	$128.83	7.567%	$138.5786	$138.58	$138.60	$138.60
Purchase #3	$71.68	6.419%	$76.2811	$76.28	$76.30	$76.30
Purchase #4	$22.90	8.506%	$24.8479	$24.85	$24.85	$24.80
Purchase #5	$112.50	4.342%	$117.3848	$117.38	$117.40	$117.40
Purchase #6	$36.51	10.391%	$40.3038	$40.30	$40.30	$40.30
Purchase #7	$82.97	8.144%	$89.7271	$89.73	$89.75	$89.70
7 purchase totals =	$648.66		$687.8497	$687.85	$687.95	$687.80