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	$118.51	11.391%	$132.0095	$132.01	$132.00	$132.00
Purchase #2	$77.86	6.158%	$82.6546	$82.65	$82.65	$82.70
Purchase #3	$68.89	4.516%	$72.0011	$72.00	$72.00	$72.00
Purchase #4	$150.71	7.855%	$162.5483	$162.55	$162.55	$162.50
Purchase #5	$171.43	9.868%	$188.3467	$188.35	$188.35	$188.30
Purchase #6	$203.89	4.238%	$212.5309	$212.53	$212.55	$212.50
Purchase #7	$155.48	9.814%	$170.7388	$170.74	$170.75	$170.70
7 purchase totals =	$946.77		$1,020.8299	$1,020.83	$1,020.85	$1,020.70