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	$181.67	10.319%	$200.4165	$200.42	$200.40	$200.40
Purchase #2	$24.42	13.516%	$27.7206	$27.72	$27.70	$27.70
Purchase #3	$194.52	12.107%	$218.0705	$218.07	$218.05	$218.10
Purchase #4	$197.79	13.458%	$224.4086	$224.41	$224.40	$224.40
Purchase #5	$138.70	12.863%	$156.541	$156.54	$156.55	$156.50
Purchase #6	$147.43	5.700%	$155.8335	$155.83	$155.85	$155.80
Purchase #7	$112.80	4.377%	$117.7373	$117.74	$117.75	$117.70
7 purchase totals =	$997.33		$1,100.7280	$1,100.73	$1,100.70	$1,100.60