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	$230.74	3.184%	$238.0868	$238.09	$238.10	$238.10
Purchase #2	$29.93	10.362%	$33.0313	$33.03	$33.05	$33.00
Purchase #3	$228.88	9.228%	$250.001	$250.00	$250.00	$250.00
Purchase #4	$132.67	10.868%	$147.0886	$147.09	$147.10	$147.10
Purchase #5	$151.84	4.780%	$159.098	$159.10	$159.10	$159.10
Purchase #6	$199.47	5.465%	$210.371	$210.37	$210.35	$210.40
Purchase #7	$79.69	12.325%	$89.5118	$89.51	$89.50	$89.50
7 purchase totals =	$1,053.22		$1,127.1885	$1,127.19	$1,127.20	$1,127.20