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	$89.51	9.432%	$97.9526	$97.95	$97.95	$98.00
Purchase #2	$59.81	12.700%	$67.4059	$67.41	$67.40	$67.40
Purchase #3	$9.69	3.134%	$9.9937	$9.99	$10.00	$10.00
Purchase #4	$50.55	8.371%	$54.7815	$54.78	$54.80	$54.80
Purchase #5	$51.88	4.820%	$54.3806	$54.38	$54.40	$54.40
Purchase #6	$169.94	12.658%	$191.451	$191.45	$191.45	$191.50
Purchase #7	$127.25	5.662%	$134.4549	$134.45	$134.45	$134.50
7 purchase totals =	$558.63		$610.4202	$610.41	$610.45	$610.60