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	$118.44	7.140%	$126.8966	$126.90	$126.90	$126.90
Purchase #2	$162.32	3.858%	$168.5823	$168.58	$168.60	$168.60
Purchase #3	$165.39	8.400%	$179.2828	$179.28	$179.30	$179.30
Purchase #4	$106.28	9.547%	$116.4266	$116.43	$116.45	$116.40
Purchase #5	$219.61	4.591%	$229.6923	$229.69	$229.70	$229.70
Purchase #6	$83.79	3.454%	$86.6841	$86.68	$86.70	$86.70
Purchase #7	$160.32	13.459%	$181.8975	$181.90	$181.90	$181.90
7 purchase totals =	$1,016.15		$1,089.4622	$1,089.46	$1,089.55	$1,089.50