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	$141.85	3.357%	$146.6119	$146.61	$146.60	$146.60
Purchase #2	$188.50	11.278%	$209.759	$209.76	$209.75	$209.80
Purchase #3	$30.80	8.155%	$33.3117	$33.31	$33.30	$33.30
Purchase #4	$200.61	9.676%	$220.021	$220.02	$220.00	$220.00
Purchase #5	$234.35	11.790%	$261.9799	$261.98	$262.00	$262.00
Purchase #6	$213.94	6.253%	$227.3177	$227.32	$227.30	$227.30
Purchase #7	$74.81	10.710%	$82.8222	$82.82	$82.80	$82.80
7 purchase totals =	$1,084.86		$1,181.8234	$1,181.82	$1,181.75	$1,181.80