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	$240.52	7.731%	$259.1146	$259.11	$259.10	$259.10
Purchase #2	$53.67	7.254%	$57.5632	$57.56	$57.55	$57.60
Purchase #3	$103.52	5.752%	$109.4745	$109.47	$109.45	$109.50
Purchase #4	$142.66	13.582%	$162.0361	$162.04	$162.05	$162.00
Purchase #5	$39.96	6.627%	$42.6081	$42.61	$42.60	$42.60
Purchase #6	$86.84	9.676%	$95.2426	$95.24	$95.25	$95.20
Purchase #7	$41.38	4.764%	$43.3513	$43.35	$43.35	$43.40
7 purchase totals =	$708.55		$769.3904	$769.38	$769.35	$769.40