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	$191.49	11.630%	$213.7603	$213.76	$213.75	$213.80
Purchase #2	$26.62	7.153%	$28.5241	$28.52	$28.50	$28.50
Purchase #3	$119.43	10.721%	$132.2341	$132.23	$132.25	$132.20
Purchase #4	$146.71	7.286%	$157.3993	$157.40	$157.40	$157.40
Purchase #5	$13.87	11.336%	$15.4423	$15.44	$15.45	$15.40
Purchase #6	$142.74	6.755%	$152.3821	$152.38	$152.40	$152.40
Purchase #7	$83.47	7.587%	$89.8029	$89.80	$89.80	$89.80
7 purchase totals =	$724.33		$789.5451	$789.53	$789.55	$789.50