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	$156.50	5.467%	$165.0559	$165.06	$165.05	$165.10
Purchase #2	$165.69	6.821%	$176.9917	$176.99	$177.00	$177.00
Purchase #3	$231.49	10.836%	$256.5743	$256.57	$256.55	$256.60
Purchase #4	$29.44	6.377%	$31.3174	$31.32	$31.30	$31.30
Purchase #5	$151.25	7.330%	$162.3366	$162.34	$162.35	$162.30
Purchase #6	$215.75	3.179%	$222.6087	$222.61	$222.60	$222.60
Purchase #7	$113.91	12.264%	$127.8799	$127.88	$127.90	$127.90
7 purchase totals =	$1,064.03		$1,142.7645	$1,142.77	$1,142.75	$1,142.80