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	$206.44	3.107%	$212.8541	$212.85	$212.85	$212.90
Purchase #2	$90.60	12.624%	$102.0373	$102.04	$102.05	$102.00
Purchase #3	$234.73	5.822%	$248.396	$248.40	$248.40	$248.40
Purchase #4	$183.41	4.439%	$191.5516	$191.55	$191.55	$191.60
Purchase #5	$136.54	4.606%	$142.829	$142.83	$142.85	$142.80
Purchase #6	$157.51	7.375%	$169.1264	$169.13	$169.15	$169.10
Purchase #7	$118.38	4.695%	$123.9379	$123.94	$123.95	$123.90
7 purchase totals =	$1,127.61		$1,190.7323	$1,190.74	$1,190.80	$1,190.70