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	$112.68	8.139%	$121.851	$121.85	$121.85	$121.90
Purchase #2	$86.99	11.465%	$96.9634	$96.96	$96.95	$97.00
Purchase #3	$48.77	9.486%	$53.3963	$53.40	$53.40	$53.40
Purchase #4	$200.88	3.736%	$208.3849	$208.38	$208.40	$208.40
Purchase #5	$243.94	8.451%	$264.5554	$264.56	$264.55	$264.60
Purchase #6	$48.76	11.294%	$54.267	$54.27	$54.25	$54.30
Purchase #7	$222.46	8.715%	$241.8474	$241.85	$241.85	$241.80
7 purchase totals =	$964.48		$1,041.2654	$1,041.27	$1,041.25	$1,041.40