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	$99.99	9.544%	$109.533	$109.53	$109.55	$109.50
Purchase #2	$26.34	4.297%	$27.4718	$27.47	$27.45	$27.50
Purchase #3	$128.32	8.758%	$139.5583	$139.56	$139.55	$139.60
Purchase #4	$141.25	12.520%	$158.9345	$158.93	$158.95	$158.90
Purchase #5	$73.64	8.121%	$79.6203	$79.62	$79.60	$79.60
Purchase #6	$211.88	6.608%	$225.881	$225.88	$225.90	$225.90
Purchase #7	$142.91	9.558%	$156.5693	$156.57	$156.55	$156.60
7 purchase totals =	$824.33		$897.5682	$897.56	$897.55	$897.60