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	$167.51	8.263%	$181.3514	$181.35	$181.35	$181.40
Purchase #2	$144.85	13.607%	$164.5597	$164.56	$164.55	$164.60
Purchase #3	$78.38	9.587%	$85.8943	$85.89	$85.90	$85.90
Purchase #4	$48.31	8.503%	$52.4178	$52.42	$52.40	$52.40
Purchase #5	$113.32	6.438%	$120.6155	$120.62	$120.60	$120.60
Purchase #6	$180.77	3.624%	$187.3211	$187.32	$187.30	$187.30
Purchase #7	$165.34	3.755%	$171.5485	$171.55	$171.55	$171.50
7 purchase totals =	$898.48		$963.7083	$963.71	$963.65	$963.70