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	$58.32	10.367%	$64.366	$64.37	$64.35	$64.40
Purchase #2	$66.34	9.861%	$72.8818	$72.88	$72.90	$72.90
Purchase #3	$231.88	11.573%	$258.7155	$258.72	$258.70	$258.70
Purchase #4	$127.89	9.591%	$140.1559	$140.16	$140.15	$140.20
Purchase #5	$125.39	8.549%	$136.1096	$136.11	$136.10	$136.10
Purchase #6	$117.94	9.697%	$129.3766	$129.38	$129.40	$129.40
Purchase #7	$250.92	5.670%	$265.1472	$265.15	$265.15	$265.10
7 purchase totals =	$978.68		$1,066.7526	$1,066.77	$1,066.75	$1,066.80