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	$148.37	12.334%	$166.67	$166.67	$166.65	$166.70
Purchase #2	$158.53	5.185%	$166.7498	$166.75	$166.75	$166.70
Purchase #3	$54.83	3.234%	$56.6032	$56.60	$56.60	$56.60
Purchase #4	$209.77	13.512%	$238.1141	$238.11	$238.10	$238.10
Purchase #5	$194.34	9.515%	$212.8315	$212.83	$212.85	$212.80
Purchase #6	$100.30	10.693%	$111.0251	$111.03	$111.05	$111.00
Purchase #7	$196.73	10.824%	$218.0241	$218.02	$218.00	$218.00
7 purchase totals =	$1,062.87		$1,170.0178	$1,170.01	$1,170.00	$1,169.90