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	$222.83	8.603%	$242.0001	$242.00	$242.00	$242.00
Purchase #2	$60.93	10.347%	$67.2344	$67.23	$67.25	$67.20
Purchase #3	$102.65	6.421%	$109.2412	$109.24	$109.25	$109.20
Purchase #4	$55.52	4.410%	$57.9684	$57.97	$57.95	$58.00
Purchase #5	$50.94	6.223%	$54.11	$54.11	$54.10	$54.10
Purchase #6	$156.90	7.410%	$168.5263	$168.53	$168.55	$168.50
Purchase #7	$89.36	6.843%	$95.4749	$95.47	$95.45	$95.50
7 purchase totals =	$739.13		$794.5553	$794.55	$794.55	$794.50