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	$173.94	7.253%	$186.5559	$186.56	$186.55	$186.60
Purchase #2	$66.45	4.664%	$69.5492	$69.55	$69.55	$69.50
Purchase #3	$95.50	5.761%	$101.0018	$101.00	$101.00	$101.00
Purchase #4	$78.27	5.282%	$82.4042	$82.40	$82.40	$82.40
Purchase #5	$148.72	13.298%	$168.4968	$168.50	$168.50	$168.50
Purchase #6	$183.90	7.704%	$198.0677	$198.07	$198.05	$198.10
Purchase #7	$160.72	13.440%	$182.3208	$182.32	$182.30	$182.30
7 purchase totals =	$907.50		$988.3964	$988.40	$988.35	$988.40