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	$178.37	8.771%	$194.0148	$194.01	$194.00	$194.00
Purchase #2	$201.26	8.371%	$218.1075	$218.11	$218.10	$218.10
Purchase #3	$29.43	6.459%	$31.3309	$31.33	$31.35	$31.30
Purchase #4	$250.99	9.524%	$274.8943	$274.89	$274.90	$274.90
Purchase #5	$80.28	11.761%	$89.7217	$89.72	$89.70	$89.70
Purchase #6	$77.71	7.827%	$83.7924	$83.79	$83.80	$83.80
Purchase #7	$169.67	11.786%	$189.6673	$189.67	$189.65	$189.70
7 purchase totals =	$987.71		$1,081.5289	$1,081.52	$1,081.50	$1,081.50