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	$93.77	9.183%	$102.3809	$102.38	$102.40	$102.40
Purchase #2	$106.99	6.850%	$114.3188	$114.32	$114.30	$114.30
Purchase #3	$217.26	3.806%	$225.5289	$225.53	$225.55	$225.50
Purchase #4	$91.51	9.824%	$100.4999	$100.50	$100.50	$100.50
Purchase #5	$102.82	6.455%	$109.457	$109.46	$109.45	$109.50
Purchase #6	$203.77	10.309%	$224.7766	$224.78	$224.80	$224.80
Purchase #7	$247.31	9.195%	$270.0502	$270.05	$270.05	$270.10
7 purchase totals =	$1,063.43		$1,147.0123	$1,147.02	$1,147.05	$1,147.10