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	$140.69	5.731%	$148.7529	$148.75	$148.75	$148.80
Purchase #2	$197.86	13.597%	$224.763	$224.76	$224.75	$224.80
Purchase #3	$136.78	10.245%	$150.7931	$150.79	$150.80	$150.80
Purchase #4	$80.43	6.702%	$85.8204	$85.82	$85.80	$85.80
Purchase #5	$118.26	9.512%	$129.5089	$129.51	$129.50	$129.50
Purchase #6	$64.41	4.236%	$67.1384	$67.14	$67.15	$67.10
Purchase #7	$157.31	4.548%	$164.4645	$164.46	$164.45	$164.50
7 purchase totals =	$895.74		$971.2412	$971.23	$971.20	$971.30