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	$52.82	3.543%	$54.6914	$54.69	$54.70	$54.70
Purchase #2	$89.80	5.219%	$94.4867	$94.49	$94.50	$94.50
Purchase #3	$194.74	11.139%	$216.4321	$216.43	$216.45	$216.40
Purchase #4	$73.25	7.326%	$78.6163	$78.62	$78.60	$78.60
Purchase #5	$243.82	4.722%	$255.3332	$255.33	$255.35	$255.30
Purchase #6	$240.43	6.250%	$255.4569	$255.46	$255.45	$255.50
Purchase #7	$61.63	5.539%	$65.0437	$65.04	$65.05	$65.00
7 purchase totals =	$956.49		$1,020.0603	$1,020.06	$1,020.10	$1,020.00