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	$115.66	13.862%	$131.6928	$131.69	$131.70	$131.70
Purchase #2	$91.76	4.447%	$95.8406	$95.84	$95.85	$95.80
Purchase #3	$215.85	10.394%	$238.2854	$238.29	$238.30	$238.30
Purchase #4	$86.56	7.228%	$92.8166	$92.82	$92.80	$92.80
Purchase #5	$90.38	9.860%	$99.2915	$99.29	$99.30	$99.30
Purchase #6	$148.66	12.798%	$167.6855	$167.69	$167.70	$167.70
Purchase #7	$228.62	7.599%	$245.9928	$245.99	$246.00	$246.00
7 purchase totals =	$977.49		$1,071.6052	$1,071.61	$1,071.65	$1,071.60