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	$162.93	8.416%	$176.6422	$176.64	$176.65	$176.60
Purchase #2	$210.32	7.864%	$226.8596	$226.86	$226.85	$226.90
Purchase #3	$165.65	12.840%	$186.9195	$186.92	$186.90	$186.90
Purchase #4	$65.93	7.436%	$70.8326	$70.83	$70.85	$70.80
Purchase #5	$74.84	4.320%	$78.0731	$78.07	$78.05	$78.10
Purchase #6	$56.88	4.644%	$59.5215	$59.52	$59.50	$59.50
Purchase #7	$236.85	11.401%	$263.8533	$263.85	$263.85	$263.90
7 purchase totals =	$973.40		$1,062.7018	$1,062.69	$1,062.65	$1,062.70