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	$185.44	3.368%	$191.6856	$191.69	$191.70	$191.70
Purchase #2	$106.80	9.443%	$116.8851	$116.89	$116.90	$116.90
Purchase #3	$187.87	11.672%	$209.7982	$209.80	$209.80	$209.80
Purchase #4	$115.77	13.652%	$131.5749	$131.57	$131.55	$131.60
Purchase #5	$135.97	13.497%	$154.3219	$154.32	$154.30	$154.30
Purchase #6	$69.53	12.694%	$78.3561	$78.36	$78.35	$78.40
Purchase #7	$47.97	5.716%	$50.712	$50.71	$50.70	$50.70
7 purchase totals =	$849.35		$933.3338	$933.34	$933.30	$933.40