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	$172.43	11.405%	$192.0956	$192.10	$192.10	$192.10
Purchase #2	$244.37	10.122%	$269.1051	$269.11	$269.10	$269.10
Purchase #3	$161.55	3.450%	$167.1235	$167.12	$167.10	$167.10
Purchase #4	$35.61	10.204%	$39.2436	$39.24	$39.25	$39.20
Purchase #5	$33.90	9.678%	$37.1808	$37.18	$37.20	$37.20
Purchase #6	$185.66	13.438%	$210.609	$210.61	$210.60	$210.60
Purchase #7	$103.88	7.526%	$111.698	$111.70	$111.70	$111.70
7 purchase totals =	$937.40		$1,027.0556	$1,027.06	$1,027.05	$1,027.00