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	$183.32	4.616%	$191.7821	$191.78	$191.80	$191.80
Purchase #2	$74.71	10.396%	$82.4769	$82.48	$82.50	$82.50
Purchase #3	$138.56	5.191%	$145.7526	$145.75	$145.75	$145.80
Purchase #4	$34.67	7.443%	$37.2505	$37.25	$37.25	$37.30
Purchase #5	$190.71	5.670%	$201.5233	$201.52	$201.50	$201.50
Purchase #6	$229.47	5.687%	$242.52	$242.52	$242.50	$242.50
Purchase #7	$174.78	3.311%	$180.567	$180.57	$180.55	$180.60
7 purchase totals =	$1,026.22		$1,081.8724	$1,081.87	$1,081.85	$1,082.00