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	$198.89	13.410%	$225.5611	$225.56	$225.55	$225.60
Purchase #2	$79.29	3.478%	$82.0477	$82.05	$82.05	$82.00
Purchase #3	$152.92	6.678%	$163.132	$163.13	$163.15	$163.10
Purchase #4	$155.83	6.850%	$166.5044	$166.50	$166.50	$166.50
Purchase #5	$152.38	4.537%	$159.2935	$159.29	$159.30	$159.30
Purchase #6	$186.34	12.413%	$209.4704	$209.47	$209.45	$209.50
Purchase #7	$72.98	4.708%	$76.4159	$76.42	$76.40	$76.40
7 purchase totals =	$998.63		$1,082.4250	$1,082.42	$1,082.40	$1,082.40