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	$78.64	8.450%	$85.2851	$85.29	$85.30	$85.30
Purchase #2	$243.82	10.262%	$268.8408	$268.84	$268.85	$268.80
Purchase #3	$63.58	3.651%	$65.9013	$65.90	$65.90	$65.90
Purchase #4	$208.28	7.872%	$224.6758	$224.68	$224.70	$224.70
Purchase #5	$95.82	4.796%	$100.4155	$100.42	$100.40	$100.40
Purchase #6	$158.43	5.526%	$167.1848	$167.18	$167.20	$167.20
Purchase #7	$229.54	6.687%	$244.8893	$244.89	$244.90	$244.90
7 purchase totals =	$1,078.11		$1,157.1926	$1,157.20	$1,157.25	$1,157.20