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	$54.68	8.411%	$59.2791	$59.28	$59.30	$59.30
Purchase #2	$233.55	3.166%	$240.9442	$240.94	$240.95	$240.90
Purchase #3	$250.62	12.258%	$281.341	$281.34	$281.35	$281.30
Purchase #4	$138.48	9.259%	$151.3019	$151.30	$151.30	$151.30
Purchase #5	$72.99	3.333%	$75.4228	$75.42	$75.40	$75.40
Purchase #6	$45.82	3.481%	$47.415	$47.42	$47.40	$47.40
Purchase #7	$191.46	4.620%	$200.3055	$200.31	$200.30	$200.30
7 purchase totals =	$987.60		$1,056.0095	$1,056.01	$1,056.00	$1,055.90