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	$154.73	7.778%	$166.7649	$166.76	$166.75	$166.80
Purchase #2	$90.32	7.443%	$97.0425	$97.04	$97.05	$97.00
Purchase #3	$155.86	10.556%	$172.3126	$172.31	$172.30	$172.30
Purchase #4	$73.93	11.339%	$82.3129	$82.31	$82.30	$82.30
Purchase #5	$161.71	9.522%	$177.108	$177.11	$177.10	$177.10
Purchase #6	$50.69	12.331%	$56.9406	$56.94	$56.95	$56.90
Purchase #7	$184.77	7.236%	$198.14	$198.14	$198.15	$198.10
7 purchase totals =	$872.01		$950.6215	$950.61	$950.60	$950.50