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	$229.55	3.591%	$237.7931	$237.79	$237.80	$237.80
Purchase #2	$87.39	4.349%	$91.1906	$91.19	$91.20	$91.20
Purchase #3	$131.95	9.840%	$144.9339	$144.93	$144.95	$144.90
Purchase #4	$141.38	7.808%	$152.419	$152.42	$152.40	$152.40
Purchase #5	$48.47	10.374%	$53.4983	$53.50	$53.50	$53.50
Purchase #6	$32.90	3.661%	$34.1045	$34.10	$34.10	$34.10
Purchase #7	$59.32	3.384%	$61.3274	$61.33	$61.35	$61.30
7 purchase totals =	$730.96		$775.2668	$775.26	$775.30	$775.20