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	$132.97	7.219%	$142.5691	$142.57	$142.55	$142.60
Purchase #2	$52.45	5.494%	$55.3316	$55.33	$55.35	$55.30
Purchase #3	$49.33	10.242%	$54.3824	$54.38	$54.40	$54.40
Purchase #4	$128.55	6.596%	$137.0292	$137.03	$137.05	$137.00
Purchase #5	$187.65	6.653%	$200.1344	$200.13	$200.15	$200.10
Purchase #6	$194.77	10.796%	$215.7974	$215.80	$215.80	$215.80
Purchase #7	$200.56	11.535%	$223.6946	$223.69	$223.70	$223.70
7 purchase totals =	$946.28		$1,028.9387	$1,028.93	$1,029.00	$1,028.90