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	$49.98	9.136%	$54.5462	$54.55	$54.55	$54.50
Purchase #2	$59.95	3.158%	$61.8432	$61.84	$61.85	$61.80
Purchase #3	$148.74	13.628%	$169.0103	$169.01	$169.00	$169.00
Purchase #4	$191.46	7.269%	$205.3772	$205.38	$205.40	$205.40
Purchase #5	$195.90	7.621%	$210.8295	$210.83	$210.85	$210.80
Purchase #6	$198.77	8.331%	$215.3295	$215.33	$215.35	$215.30
Purchase #7	$201.82	3.748%	$209.3842	$209.38	$209.40	$209.40
7 purchase totals =	$1,046.62		$1,126.3201	$1,126.32	$1,126.40	$1,126.20