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	$245.42	4.229%	$255.7988	$255.80	$255.80	$255.80
Purchase #2	$26.47	12.811%	$29.8611	$29.86	$29.85	$29.90
Purchase #3	$131.62	4.596%	$137.6693	$137.67	$137.65	$137.70
Purchase #4	$221.82	13.470%	$251.6992	$251.70	$251.70	$251.70
Purchase #5	$42.97	8.570%	$46.6525	$46.65	$46.65	$46.70
Purchase #6	$86.68	4.270%	$90.3812	$90.38	$90.40	$90.40
Purchase #7	$184.27	3.459%	$190.6439	$190.64	$190.65	$190.60
7 purchase totals =	$939.25		$1,002.7060	$1,002.70	$1,002.70	$1,002.80